+ltleelim Posted October 19, 2007 Share Posted October 19, 2007 My wife and I are adding a few more pieces of benchmark hunting gear. We've recently encountered situations where we needed to probe and dig. It wasn't that hard to find suitable items for probing (12" screwdriver) and digging (plastic trowel). However, we could also use a decent 50' measuring tape, but I'm having a hard time finding anything suitable for us. We often hike or backpack to survey markers so we need something lightweight and compact. The lightest 50' tape I've found is the Lufkin 3/8" x 50' Hi-Viz Universal Lightweight Long Steel Tape. It only weighs 0.5 lbs (comparable to a typical household tape measure), but it is 7" x 5" which is too big for us to carry on hikes. The CST/berger MeasureMark 50' Depth Gauge Tape looked promising, until they told me it weighs 1 lb. It shouldn't be that hard. I figure that a 50' length of truly lightweight tape, made out of something like Tyvek, should fit on a small plastic spool and weigh only a few ounces. You could probably even make a 100' tape like this weighing well under a half pound. Does anyone make something like this? Lloyd Quote Link to comment
2oldfarts (the rockhounders) Posted October 19, 2007 Share Posted October 19, 2007 Have you considered using your GPSr as your backpacking measuring device? You just set a waypoint for the spot you want to measure from and then walk in the direction you need and set a goto for the waypoint you just made. Your GPSr will tell you how far it is to your waypoint and the direction, just add 180 degrees to what the GPSr is showing to tell if you're going in the right direction. When the GPSr says you are at the distance wanted and the bearing is right you will be very close to the correct spot. Try doing this in your back yard to see how well you do. John Quote Link to comment
+DonB Posted October 19, 2007 Share Posted October 19, 2007 My wife and I are adding a few more pieces of benchmark hunting gear. We've recently encountered situations where we needed to probe and dig. It wasn't that hard to find suitable items for probing (12" screwdriver) and digging (plastic trowel). However, we could also use a decent 50' measuring tape, but I'm having a hard time finding anything suitable for us. We often hike or backpack to survey markers so we need something lightweight and compact. The lightest 50' tape I've found is the Lufkin 3/8" x 50' Hi-Viz Universal Lightweight Long Steel Tape. It only weighs 0.5 lbs (comparable to a typical household tape measure), but it is 7" x 5" which is too big for us to carry on hikes. The CST/berger MeasureMark 50' Depth Gauge Tape looked promising, until they told me it weighs 1 lb. It shouldn't be that hard. I figure that a 50' length of truly lightweight tape, made out of something like Tyvek, should fit on a small plastic spool and weigh only a few ounces. You could probably even make a 100' tape like this weighing well under a half pound. Does anyone make something like this? Lloyd I have a 50' Stanley that weighs 6.8 ounces and measures 3 1/8" x 3 5/8". I've had this one for awhile so I can't say if they still make it or not. The number on it is 34-383, which I assume is their part number. Quote Link to comment
+Lunatic728 Posted October 19, 2007 Share Posted October 19, 2007 Get some pink masonary string and tie knots every foot or 2 or if you perfer tie knots every meter. Make it as long as you like. It weighs almost nothing, and costs almost nothing. Heck you can shove it in your pocket. If you really want to wrap a piece of duct tape every so often with the coresponding mesurement this way you don't have to count from the begining. There is my .02 and about the cost of my backyard tape measure. Lunatic Quote Link to comment
+Black Dog Trackers Posted October 19, 2007 Share Posted October 19, 2007 (edited) I bought an old 50 foot tape in an antique store for about $15. The closed reel is pretty light (non-metallic) and the tape is made of canvas, so it is very light. The best thing about it is that it is a surveyors tape, marked in feet and 1/10s of a foot. My wife bought me a 100 foot steel tape in an antique store a couple years previously, so if I need 100 feet I can bring that, but it is about 5x as heavy and the same physical size. Canvas tapes stretch a bit of course, but it's not so bad for benchmark hunting. While I'm saying this, I also bought a 12-foot folding carpenters ruler in an antique store (I go to a lot of them!). It is an aluminum one and is very handy for solo benchmark hunting to measure distances from curb faces, trees, etc. without having to stake out a tape. My very lightest tape of course is the Ikea 39" (metric on the reverse) paper tape that's folded up in my wallet. In a pinch, this tape and a rock or two can be used to measure distances of several feet. Edited October 19, 2007 by Black Dog Trackers Quote Link to comment
+wvhillbilly59 Posted October 19, 2007 Share Posted October 19, 2007 just add 180 degrees to what the GPSr is showing to tell if you're going in the right direction 2oldfarts, I don't quite understand what you mean by that. I've been using the GPS lately just as you suggest and sometimes it gets right on the mark and sometimes not even close. Thanks. Quote Link to comment
2oldfarts (the rockhounders) Posted October 19, 2007 Share Posted October 19, 2007 just add 180 degrees to what the GPSr is showing to tell if you're going in the right direction 2oldfarts, I don't quite understand what you mean by that. I've been using the GPS lately just as you suggest and sometimes it gets right on the mark and sometimes not even close. Thanks. If the object that you are trying to find is 90° from your reference point, then when you set your goto for that reference point you will need to add 180° to the bearing the GPSr says you need to take to get to the reference point. When you set the waypoint and start walking 90° according to your compass, your GPSr will read that you need to take a bearing of 270° to get to your waypoint. But since you want to go away from your waypoint you need to add 180° to what the GPSr says your bearing should be. If you know the angle from the benchmark 'to' your reference point then you can use that bearing on your GPSr. For example, your reference point is 125° from the station disk, you just set the goto and follow the bearing of 125° to the reference point, when you reach the correct distance, you start looking for the disk or any sign of it. If you know the angle from the station disk to the reference point then use that as the bearing. If you know the angle from the reference point to the station disk, then add 180° to it, so you go in the correct direction. John Quote Link to comment
+ltleelim Posted October 19, 2007 Author Share Posted October 19, 2007 Have you considered using your GPSr as your backpacking measuring device? You just set a waypoint for the spot you want to measure from and then walk in the direction you need and set a goto for the waypoint you just made. Your GPSr will tell you how far it is to your waypoint and the direction, just add 180 degrees to what the GPSr is showing to tell if you're going in the right direction. When the GPSr says you are at the distance wanted and the bearing is right you will be very close to the correct spot. First, I think if I was going to do that, then I would project a waypoint instead of turning around and pointing at where I used to be. It's not a bad idea, but we only resort to measuring when we can't easily find the marker. So we're measuring stuff like 35 feet from the centerline of an old road. Inches don't matter, but 5 feet of error would make a big difference. We can't get that accurate with a handheld GPS in rough terrain and under tree cover. Thanks for the suggestion though, Lloyd Quote Link to comment
+Renegade Knight Posted October 19, 2007 Share Posted October 19, 2007 Have you considered using your GPSr as your backpacking measuring device? You just set a waypoint for the spot you want to measure from and then walk in the direction you need and set a goto for the waypoint you just made. Your GPSr will tell you how far it is to your waypoint and the direction, just add 180 degrees to what the GPSr is showing to tell if you're going in the right direction. When the GPSr says you are at the distance wanted and the bearing is right you will be very close to the correct spot. First, I think if I was going to do that, then I would project a waypoint instead of turning around and pointing at where I used to be. It's not a bad idea, but we only resort to measuring when we can't easily find the marker. So we're measuring stuff like 35 feet from the centerline of an old road. Inches don't matter, but 5 feet of error would make a big difference. We can't get that accurate with a handheld GPS in rough terrain and under tree cover. Thanks for the suggestion though, Lloyd That depends on the error. If GPS error is systematic. The 5' error won't matter one whit since you will have already accounted for it when you stood on the spot you needed to mark your waypoint. If it's random...that's another thing. I'm not 100% sure which GPS is, or if it's a mix of both error types. Quote Link to comment
+wvhillbilly59 Posted October 19, 2007 Share Posted October 19, 2007 just add 180 degrees to what the GPSr is showing to tell if you're going in the right direction 2oldfarts, I don't quite understand what you mean by that. I've been using the GPS lately just as you suggest and sometimes it gets right on the mark and sometimes not even close. Thanks. If the object that you are trying to find is 90° from your reference point, then when you set your goto for that reference point you will need to add 180° to the bearing the GPSr says you need to take to get to the reference point. When you set the waypoint and start walking 90° according to your compass, your GPSr will read that you need to take a bearing of 270° to get to your waypoint. But since you want to go away from your waypoint you need to add 180° to what the GPSr says your bearing should be. If you know the angle from the benchmark 'to' your reference point then you can use that bearing on your GPSr. For example, your reference point is 125° from the station disk, you just set the goto and follow the bearing of 125° to the reference point, when you reach the correct distance, you start looking for the disk or any sign of it. If you know the angle from the station disk to the reference point then use that as the bearing. If you know the angle from the reference point to the station disk, then add 180° to it, so you go in the correct direction. John Oh, Duh! Ok, I guess I just subconsciously allowed for that without thinking about it when going off the center of a road or from a RM. Seems since I turned the big 60 I do a lot of things subconsciously, or even unconsciously. Thanks for explaining it so I didn't think I was missing something. Quote Link to comment
+ltleelim Posted October 19, 2007 Author Share Posted October 19, 2007 Get some pink masonary string and tie knots every foot or 2 or if you perfer tie knots every meter. Make it as long as you like. It weighs almost nothing, and costs almost nothing. Heck you can shove it in your pocket. If you really want to wrap a piece of duct tape every so often with the coresponding mesurement this way you don't have to count from the begining. There is my .02 and about the cost of my backyard tape measure. Thanks, that's a great idea. I did think about tying knots in fishing line, but counting the knots would probably drive my wife crazy. The simple idea of taping on numbers makes it much more usable. I never heard of masonry string before, but I see that it's a durable nylon, a nice bright pink (easier to see than fishing line), and it comes on handy reels (which we might even use if they aren't too big or heavy). We could easily carry 100' of that. Thanks! Lloyd Quote Link to comment
+ltleelim Posted October 19, 2007 Author Share Posted October 19, 2007 It's not a bad idea, but we only resort to measuring when we can't easily find the marker. So we're measuring stuff like 35 feet from the centerline of an old road. Inches don't matter, but 5 feet of error would make a big difference. We can't get that accurate with a handheld GPS in rough terrain and under tree cover. That depends on the error. If GPS error is systematic. The 5' error won't matter one whit since you will have already accounted for it when you stood on the spot you needed to mark your waypoint. If it's random...that's another thing. I'm not 100% sure which GPS is, or if it's a mix of both error types. GPS has both kinds of errors, but we often see fluctuating reception with Yosemite's terrain and trees. We wouldn't be able to measure like that when the reading is constantly changing. I always take readings at markers, but I often have to wait 5 minutes or so for a good lock. Once in a while, we have to come back to try again with a different constellation. Reception is wonderful when we're above the treeline. But then the markers are on bare granite, so we never need to measure to find them. Lloyd Quote Link to comment
+Black Dog Trackers Posted October 19, 2007 Share Posted October 19, 2007 I would not recommend using a handheld GPS to measure to a mark unless: the measurement required was several hundred feet away and taping would be impractical the mark to find ended up being visible from the surface without having to dig for it you're going to use a metal detector, so searching a hundred square foot area is practical There's just too much random error with a handheld GPS to use it if you're going to have to dig without a metal detector to tell you where to dig. A few months ago I took a bunch of data on this but haven't yet done the analysis or posted that here. I guess I should get the notes and do it. Quote Link to comment
Wintertime Posted October 19, 2007 Share Posted October 19, 2007 If you know the angle from the benchmark 'to' your reference point then you can use that bearing on your GPSr. For example, your reference point is 125° from the station disk, you just set the goto and follow the bearing of 125° to the reference point, when you reach the correct distance, you start looking for the disk or any sign of it. Your GPS receiver must be a lot more accurate than mine, John! Although there are times when it's spot on (in fact, I just used the above method to find a nanocache the other day), at other times, it can be off by 30 feet. I can understand why Lloyd wants a tangible measuring device. Patty Quote Link to comment
Wintertime Posted October 19, 2007 Share Posted October 19, 2007 (edited) [Groundspeak's web server told me it had timed out the first time I tried to post this. Since I can't delete the extra, thought I'd post an explanation. :-) ] Edited October 20, 2007 by Wintertime Quote Link to comment
mloser Posted October 19, 2007 Share Posted October 19, 2007 I have never thought of weight being an issue, but when I hunt all I really carry is my backpack full of hunting tools and a bottle of water. I only rarely walk any major distances (and when I do I plan accordingly), so my backpack just has hunting tools in it. This image is a couple months old and a few things have changed, but this is what I carry with me whenever I get out of the car, with some exceptions I will explain. At the top are two metal detectors. I only ever carry one, and that one is invariably the lower one in the photo--my cheapie that is even small enough to compact down so that I can stick it in the backpack, albeit with the round detector head sticking out like some oddball antenna. At the left is my backpack, since replaced by a similar model, as this one lost a strap when I tried to schlep a 57 lb monument from KW2987. Next to that is my tape measure. I haven't even thought of how big it is, or isn't. It is 100 ft, marked in inches and tenths, and was a cheap one from Home Depot. It has survived well considering the type of use it gets. Beside it are two spikes I use to hold down the dumb end when I need to. Next is my camp shovel. It is the single heaviest thing in the bag, but I never leave it behind because historically that was when I needed it most. I often need to arrange it in the bag so it doesn't poke me in the back though. I have a machete too, but tend to leave it in the car much of the time as I think it looks a bit aggressive. Typically those are the times I could use it most and end up hacking at some bush with the shovel. There is no easy way to carry the machete without it being noticeable--it sticks up out of the pack when I put it in there. So I take it only when I feel I have to. The smaller items to the right are: a small plastic shovel, which is VERY useful, and has replaced the bigger shovel about 90 percent of the time for small digging and getting rid of moss, etc. Too bad I left it somewhere and need a new one. The pliers have been used only a couple of times, to open a pipe cap over a mark, but have proved invaluable and take up little space. The brush is used all the time to clean off marks. I have 3 compasses and just grab the first one I see. They are interchangeable. Finally, the pink string/yarn and the gray thing in the bag... these were used when trying to locate the centerpoint of a very old tri-station that was located in the center of 4 reference holes. The gray thing in the bag is clay and I used it to hold the string down on rock surfaces to form the crosses that marked the tri-station. The hunt was not a success but I left the things in my bag because they weigh nearly nothing. And the white thing at the top is an old t-shirt for final wiping of benchmarks. Now, I am not advocating carrying all this junk around. It's just the way I operate. Quote Link to comment
2oldfarts (the rockhounders) Posted October 19, 2007 Share Posted October 19, 2007 It's not a bad idea, but we only resort to measuring when we can't easily find the marker. So we're measuring stuff like 35 feet from the centerline of an old road. Inches don't matter, but 5 feet of error would make a big difference. We can't get that accurate with a handheld GPS in rough terrain and under tree cover. That depends on the error. If GPS error is systematic. The 5' error won't matter one whit since you will have already accounted for it when you stood on the spot you needed to mark your waypoint. If it's random...that's another thing. I'm not 100% sure which GPS is, or if it's a mix of both error types. GPS has both kinds of errors, but we often see fluctuating reception with Yosemite's terrain and trees. We wouldn't be able to measure like that when the reading is constantly changing. I always take readings at markers, but I often have to wait 5 minutes or so for a good lock. Once in a while, we have to come back to try again with a different constellation. Reception is wonderful when we're above the treeline. But then the markers are on bare granite, so we never need to measure to find them. Lloyd We have been using this method for quite some time now and have found numerous benchmarks. The error factor doesn't come into play unless you are taking a long time to measure out the distance. By long time I mean several hours from the time that you set the waypoint. If the description says the mark is 135 feet from the center line of the highway, I just walk out to the center (when there is no traffic!), set a waypoint, start walking in the direction needed and do the goto for that waypoint just set. When the GPSr says I have gone the correct distance I make a mark on the ground and start looking for other objects in the description. Here's an example of one where we used the GPSr to located the buried benchmark. Please note in the description that no exact angle is given for any of the ties/reference points. It was necessary first to measure from the highway in 2 different places and establish a line the needed distance from the highway. Then we could measure from the pole and where the correct distance intersected with that line is where we began our search, using both a metal detector and a probe. This method has worked for us also in the National Forest on the Kaibab Plateau with heavy tree covering. Using this method is like pacing the distances needed, some folks can do it and others just can't seem to grasp the technique. If it works for you it will save carrying extra weight in the backpack. If not, hope you can find something light to carry. And for the record, we're using a Magellan Meridan Platinum. John Quote Link to comment
+Harry Dolphin Posted October 19, 2007 Share Posted October 19, 2007 I did locate an RM using the 2oldfarts method! But for 28' from the third post of the guardrail, and 64' from the blazed oak tree, I like my 100' steel ruler. It weigh 16 oz. Not a lot of weight in my backpack. Quote Link to comment
+t8r Posted October 20, 2007 Share Posted October 20, 2007 Stanley 34-450. 4"X 3 1/4" Quote Link to comment
+t8r Posted October 20, 2007 Share Posted October 20, 2007 Stanley 34-450. 4"X 3 1/4" steel tape 7oz. Quote Link to comment
NGS Surveyor Posted October 22, 2007 Share Posted October 22, 2007 Most REFERENCE MARKS are within 100 feet of the main station (per USC&GS/NGS specs), so I would use a cloth or fiberglass, 100 foot measuring tape. Its light, simple, and accurate enough. Regarding probing, survey crews have used "tile probes" for years. Just do a www search for "tile probe" and you will find some listed. They are typically a steel rod about 4 feet long with a handle to push them into the ground and to pull them back out. I like the photo with the recovery gear, and suggest this group make up a list starting with the equipment in the photo. Could add something to highlight the disk stamping, and, of course, the camera! GEL Quote Link to comment
+Black Dog Trackers Posted October 22, 2007 Share Posted October 22, 2007 I like the photo with the recovery gear, and suggest this group make up a list starting with the equipment in the photo. There is such a list in the Benchmark Search and FAQ page and here it is. There are also numerous topics from the past that have discussed benchmark hunting equipment and lists of equipment, and some that just discussed different kinds of probes. Quote Link to comment
+ltleelim Posted November 6, 2007 Author Share Posted November 6, 2007 This is a follow-up regarding the various gear suggestions. Thanks for the suggestions! I like searching online for information, but I also like looking at things in person because things aren't always the same in real life. Several of the suggested items were a bit different than we expected. I previously mentioned that the Lufkin 3/8" x 50' Hi-Viz Universal Lightweight Long Steel Tape is too big at 7" x 5". It turns out that those are the dimensions of the packaging. The Lufkin tape is really 3.75" x 3.25", which is nice and compact. However, it turns out there is something lighter. It looks like they don't make the Stanley 34-383 or Stanley 34-450 anymore. We ended up choosing the Stanley 34-103 50' x 3/8" Long Tape Rule, which weighs 7.0 oz. It is the same size as the Lufkin tape, but it is lighter and it has a slightly thinner profile. Masonry string was a great idea, but it was too bulky in real life. For an ultralight solution, I would recommend tying knots in fishing line and taping on numbers every five feet. 100' of fishing line on a small spool probably would weigh only a couple ounces. If we were going on a long backpacking trip, I might do this. Regarding tile probes, the smallest one I've seen is 3 feet long. This is absolutely out of the question for hiking or backpacking use. My wife and I recently hiked to Bald Mountain in Yosemite to recover a marker on the summit. A tile probe would have snagged every other step in the dense brush. I am not exaggerating. We are currently using a Craftsman 1/4" x 12" Slotted Screwdriver for probing, which weighs 5.8 oz. It works great in forest floor. We haven't tried it in hard packed ground yet. I like how we could also use it to lift up monument covers and how it has a lifetime warranty in case we accidentally bend it. Quote Link to comment
+ltleelim Posted November 6, 2007 Author Share Posted November 6, 2007 This is a follow-up regarding the suggestion to use your GPS receiver to measure distances. My wife and I are not beginners. We fully understand the concept, but I was skeptical about the accuracy of this method. However, because of the potential weight savings, I tested this method with an open mind. Please keep in mind that when my wife and I need to measure, it's usually because we really need to measure. We really need to measure when (1) the marker appears to be buried and we need to probe and dig or (2) the marker appears to be missing and we're looking for a drill hole. My test case was in Yosemite National Park. The marker is described as 35 feet off the centerline of an old road. There are no other references to use, so we were faced with searching a hundred foot long section. There is moderate forest cover. The immediate search area is flat, but the surrounding terrain is hilly. We have a Garmin 60CS, if that makes any difference. At the first test point, I saved a waypoint (EPE was +/- 16 feet), did a goto to the waypoint, and walked away from the centerline until the distance read 35 feet. Then my wife and I measured the actual distance with a tape measure. The actual distance was 19 feet, an error of 16 feet. When I walked back to the waypoint and stood there, it said I was 33 feet away from the waypoint. Utterly useless. At the second test point, I averaged a waypoint for 60 seconds to try to get better accuracy. I had locks on 10 satellites and was receiving WAAS corrections for all of them. The averaged EPE was +/- 6.6 feet. Again, I walked away until the goto said I was 35 feet away. The actual distance was 40 feet away, an error of 5 feet. Much better. Personally, this method is unacceptable for our purposes. To probe a 100' line for a 6" x 6" concrete post, we are faced with sticking a probe in the ground about 200 times. If we also probe 6" on both sides of the line to compensate for possible sloppiness in our use of the measuring tape, we're faced with probing 600 times. If we used the goto method and had to compensate for errors of up to +/- 5 feet, then we'd have to probe about 4200 times. We'd rather carry a tape. In fact, I'd have better accuracy by pacing. Nevertheless, this method might be ok for some people. If you're using it just as a rough guideline for a visual search, that'd be fine. If you don't have trees or terrain interfering with your reception, you might have better results. Quote Link to comment
2oldfarts (the rockhounders) Posted November 6, 2007 Share Posted November 6, 2007 This is a follow-up regarding the suggestion to use your GPS receiver to measure distances. My wife and I are not beginners. We fully understand the concept, but I was skeptical about the accuracy of this method. However, because of the potential weight savings, I tested this method with an open mind. Please keep in mind that when my wife and I need to measure, it's usually because we really need to measure. We really need to measure when (1) the marker appears to be buried and we need to probe and dig or (2) the marker appears to be missing and we're looking for a drill hole. My test case was in Yosemite National Park. The marker is described as 35 feet off the centerline of an old road. There are no other references to use, so we were faced with searching a hundred foot long section. There is moderate forest cover. The immediate search area is flat, but the surrounding terrain is hilly. We have a Garmin 60CS, if that makes any difference. At the first test point, I saved a waypoint (EPE was +/- 16 feet), did a goto to the waypoint, and walked away from the centerline until the distance read 35 feet. Then my wife and I measured the actual distance with a tape measure. The actual distance was 19 feet, an error of 16 feet. When I walked back to the waypoint and stood there, it said I was 33 feet away from the waypoint. Utterly useless. At the second test point, I averaged a waypoint for 60 seconds to try to get better accuracy. I had locks on 10 satellites and was receiving WAAS corrections for all of them. The averaged EPE was +/- 6.6 feet. Again, I walked away until the goto said I was 35 feet away. The actual distance was 40 feet away, an error of 5 feet. Much better. Personally, this method is unacceptable for our purposes. To probe a 100' line for a 6" x 6" concrete post, we are faced with sticking a probe in the ground about 200 times. If we also probe 6" on both sides of the line to compensate for possible sloppiness in our use of the measuring tape, we're faced with probing 600 times. If we used the goto method and had to compensate for errors of up to +/- 5 feet, then we'd have to probe about 4200 times. We'd rather carry a tape. In fact, I'd have better accuracy by pacing. Nevertheless, this method might be ok for some people. If you're using it just as a rough guideline for a visual search, that'd be fine. If you don't have trees or terrain interfering with your reception, you might have better results. Sorry your Garmin doesn't do well using this method. We use a Magellan Meridian Gold & a Magellan Meridian Platinum for this. It doesn't matter where since we have used this method in both open terrain and in National forest to find benchmarks. Maybe it's a Garmin thing. There is also pacing for shorter (under 100 feet) distances. John Quote Link to comment
+ltleelim Posted November 6, 2007 Author Share Posted November 6, 2007 Sorry your Garmin doesn't do well using this method. We use a Magellan Meridian Gold & a Magellan Meridian Platinum for this. It doesn't matter where since we have used this method in both open terrain and in National forest to find benchmarks. Maybe it's a Garmin thing. I do know that Magellan units use an automatic averaging filter when you are stationary. This feature might help you when using this method. (The Magellan automatic averaging cannot be disabled. I always take averaged readings at survey markers and want manual control over averaging, so I bought a Garmin instead.) Have you ever tested your method in the field to see what your actual accuracy is? From your previous posts, you apparently use this method as a starting point for a visual search and that you also use a metal detector. Both uses would compensate for any error. I'm guessing that the actual measured error is greater than you might realize. As I mentioned, I tested this method to find a starting point for blind probing, which is a more demanding situation. I don't think any handheld unit is good enough for that. Quote Link to comment
2oldfarts (the rockhounders) Posted November 6, 2007 Share Posted November 6, 2007 [ Have you ever tested your method in the field to see what your actual accuracy is? From your previous posts, you apparently use this method as a starting point for a visual search and that you also use a metal detector. Both uses would compensate for any error. I'm guessing that the actual measured error is greater than you might realize. As I mentioned, I tested this method to find a starting point for blind probing, which is a more demanding situation. I don't think any handheld unit is good enough for that. Sorry you have not had any luck using this method. Perhaps we have the only GPSr that can accurately measure how far we have traveled from point a to point b. I can't say how many benchmarks we have recovered using this many, but I can say, we have been quite successful using this method. The few times I actually measured the distance with a 100' metal tape, I was within just a foot or two of what the GPSr said. This was for measurement in the 50' to 75' range. If your unit was off 50% (19' instead of 35') you may have a defective unit. The GPSr should be able to show the distance you have moved from point a to point b if the move was done over a very short period of time. Short period of time being, setting the waypoint and then immediately making the measurement. If you set the waypoint and then wait a while things will change and the results will not be as accurate. In any case, if your unit will not perform this function your best bet is to NOT use it. Stick with what works for you. John Quote Link to comment
+ltleelim Posted November 10, 2007 Author Share Posted November 10, 2007 If your unit was off 50% (19' instead of 35') you may have a defective unit. As I mentioned previously, the unit was displaying an EPE of +/- 16 feet when I saved the waypoint and started walking. Under these conditions, a goto distance error of 16 feet cannot be characterized as off by 50%. Although we could start talking about GPS error, EPE, RMS, and CEP, that would probably be futile. Quote Link to comment
2oldfarts (the rockhounders) Posted November 10, 2007 Share Posted November 10, 2007 If your unit was off 50% (19' instead of 35') you may have a defective unit. As I mentioned previously, the unit was displaying an EPE of +/- 16 feet when I saved the waypoint and started walking. Under these conditions, a goto distance error of 16 feet cannot be characterized as off by 50%. Although we could start talking about GPS error, EPE, RMS, and CEP, that would probably be futile. Actually it can be characterized as almost 50 % off, since the EPE stays pretty much the same in the time frame it takes to walk 10 paces. Even with EPE in the 15' to 25' range, our GPSr will still read well under 10' when standing at an adjusted benchmark. The EPE is what the GPSr thinks its error "could" be, and that is usually different from what the actual error is. Your unit should be able to measure a change of 30 feet in its position and be within +/- 3 feet if you set the waypoint and immediately measure that distance. Perhaps you should compare your unit to those of your friends to see how much difference there is in GPSr units. Simply compare the position coordinates with other GPSr all sitting next to each other and see if they read the same. If not how much of a difference is there? If you don't trust your GPSr to give accurate readings then definitely don't bother trying to make any measurements using it and stick to using some other measuring device. This use of a GPSr is not for everyone, so don't feel bad if your unit doesn't Measure up. John Quote Link to comment
+frex3wv Posted November 19, 2007 Share Posted November 19, 2007 Since I go on many of my benchmark hunts alone - I need a good measuring device. Please follow this link below and give me feedback on if this would be a good choice (going to be asking for it for Christmas) if it is) - and if not what would work better? Please note - not sure how big it is - but I don't mind packing it in if it will work well. http://www.hammerdownwoodproducts.com/inde...2f5be64f6baf2d0 Quote Link to comment
+Black Dog Trackers Posted November 19, 2007 Share Posted November 19, 2007 (edited) frex3wv - That's a good type of tape to use. I use the closed-reel version of the same thing. The end of the tape has a square loop and I carry a stiff wire in my pack that I can stick in the ground to hold the end of the tape. I recommend the feet-and-tenths version of course. Those come in 300 foot lengths too but that is too long for almost all benchmark hunting needs. They also come in 50 foot lengths which is long enough maybe 75%-or-more of the time, but the 100 foot length is probably the best size to get. Edit to add that the 100 foot length is about 8" in diameter (the yellow tape part only). (What's pictured there is actually the 300 foot version.) Edited November 19, 2007 by Black Dog Trackers Quote Link to comment
+frex3wv Posted November 19, 2007 Share Posted November 19, 2007 thanks for the input BDT! Is closed reel better? are they more expensive? Quote Link to comment
+Harry Dolphin Posted November 19, 2007 Share Posted November 19, 2007 Frex, that's listed as 5#! Think my tape meaure is closer to 1#. ltleelim, I use a 12" screwdriver. I generally figure that if the disk is buried more than that, I ain't gonna find it anyway. It does not work well in 'refusal' (gotta love that word!), or in compacted dirt with rocks. Oh, well. Move on to the next station. I'm not into doing a lot of digging in that type of soil anyway. (Okay, there is still Springfield Reset. I will find that one! It is buried up to a foot under the trail, with ballast for the trail surface.) Quote Link to comment
+Black Dog Trackers Posted November 20, 2007 Share Posted November 20, 2007 frex3wv - The one I use is this: http://www.stakemill.com/store/index.php?m...products_id=329 except I have the 50-foot model. It isn't totally closed. My 100-foot tape is steel and is quite heavy and looks about like this: http://www.toolup.com/productinfo.asp?pid=...1-D0E443A8CF70} except it is an antique. Quote Link to comment
+GEO*Trailblazer 1 Posted November 20, 2007 Share Posted November 20, 2007 I have a cheap 100' roll up cloth tape. It is about 1/2#. I can't remember where I got it though. It works great for long hikes. Quote Link to comment
+frex3wv Posted November 20, 2007 Share Posted November 20, 2007 BDT: so which would you suggest - the one I linked to or the 1st one you linked to? Quote Link to comment
+Black Dog Trackers Posted November 20, 2007 Share Posted November 20, 2007 frex3wv - Oh sorry, I was going to say that the one you linked to will be fine. Keson is a good brand; here is their website. As you can see, the model number you're considering is the OTR10100. There is a model with feet-and-tenths on one side and metric on the other (OTR10M100) but I don't recommend that because it can be confusing sometimes. I didn't look for that model number on the internet. I'm assuming that the datasheets you'll be working with are all in feet-and-tenths for the reference marks and reference objects, so the OTR10100 with one side of the tape blank will be good. If you'll have some metric work to do, then the feet-and-metric tape is what you should look for. Here is another site with the same price as yours with a couple more sizes. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.