VirginiaJim

I live in Greene County Virginia in the town of Ruckersville. Hightway 33 runs between Ruckersville and Standardsville Virginia. A few years ago it was widened to four lanes. The majority of the benchmarks along the highway are gone, or least I am going to have to log them as DNF for now. I am finding a lot of VDOT right of way markers at various intersections. I guess progress and new construction affects all areas, city, county, or rural.

I am just starting out in benchmarking. I believe I have found the correct location for this benchmark, HW0562. It appears that the bench mark disk is gone and only the concrete monument remains. I have included a picture with the GPS unit averaging for ten minutes. I am also unable to find HW0563 Rucker RM 1 and HW0564 Rucker RM 2 in the same area. However, I plan to return to search for them again. How would I log this for HW0562

Now how do you set a compass to UTM, they are either True or Magnetic. I believe the difference was Magnetic (Field Bearing) and True (Map Bearing). I use a Suunto M3 most of the time. "The M-3 is a top rank compass with a large liquid filled capsule and sapphire jeweled bearing. The compass features a serrated bezel ring, which is easy to turn even in cold weather when wearing gloves. The M-3 has an adjustable declination correction scale." At the bottom of USGS quad maps is the declination diagram. It shows true, GN (grid north) and MN (magnetic north). A local map quad, Swift Run Gap, VA shows a GM (grid/magnetic) angle of 11 degrees. You adjust the declination on the compass to match GN just like you would MN.

I prefer to use UTM for backcountry hiking and geocaching. Many of the USGS maps now have UTM coordiantes and/or lines. The Shenandoah National Park maps also have UTM coordinates marked on them. I use a UTM corner ruler in preparing for goecaching and during the hunt. I often can locate the cache without a GPS unit this way. My Garmins easily switch to UTM. I also set my compass for UTM to avoid any conversions in the field. The NG program sure looks nice.

That is an interesting question. While looking for geocaches I use WGS84 most of the time. However, I use NAD27 while using USGS quad maps. The maps are drawn with the NAD 27 datum. The accuracy between these two datums is always right on. I often use UTM coordinates, because I like meters and I mark my USGS maps in UTM grids. It is much easier for me to plot UTM on a map. I notice no difference in accuracy between the different coordinate systems of latitude/longitude and UTM while geocaching. I will use latitude/longitude in the field when multi caches use them. I notice no difference using the three different ways of representing latitude/longitude. They all get me to the same spot. I use the Garmin Extex Vista and the Map76s. So, I see no difference when hunting for geocaches.

I have made several post regarding accuracy. In fact, I made a post quoting a source that was one of the first to explain why distance from the ground station was not a issue with WAAS accuracy. "The primary factor is spatial decorrelation, which is the degradation of corrections due to separation from the reference station. RTCM based DGPS corrections suffer from spatial decorrelation, but WAAS corrections do not." During the course of the discussion I additionally suggested and talked about limitations of WAAS with our handheld GPS units. In each case I have quoted sources including Garmin to discuss this issues with WAAS and our units. " To broaden the scope to include issues (mapping speed & power consumption) that have nothing to do with my original premise (accuracy) in order to discredit my integrity is truly immature. So stop attacking me with petty nonsense, but feel free to address "exactly" what I stated as fact with facts." I'm not sure why it is taboo to broaden the scope of the discussion. We already agree on the subject of accuracy. When I quote a source it is to have it considered and discussed. The orginal premise was not even yours. It was: "Do you recomend using WAAS or Not using it?" Discussing the effect of WAAS on mapping speed is a factor to consider in using or not using it. As for your integrity, we proabably shouldn't discuss that here. Let's you and I concentrate on the discussion of WAAS.

So we agree that distance from the ground stations is not a factor? Most seem to agree that WAAS, like any technology has limitations? How about that there can be a degradation of the gps units performance using WAAS under certain conditions which you and I are often in while geocaching according to Garmin?

I will not belabor the point that you can discuss things without screaming FACT, name calling, and a condesending attitude. Manners and maturity here and elsewhere speak for themselves. They are also qualities that will encourage others to listen to your "FACTS." From the Garmin Etrex Manual What do you think? Garmin is speaking about the limitations of WAAS and the negative effect on their GPS units. A degradation of the units ability to draw maps. Therefore, a reason not to use WAAS in these situations. So, even the makers of these units at Garmin believe there can be a degradation of the performance of their units with WAAS under certain conditions. Exactly what my original post and quotes suggested. Don't get upset with me for posting a quote from Garmin. I'm just asking you to consider that they may be right. That your "FACTS" might be incorrect.

I own a Vista and a GPSMAP 76S. I enjoy the electronic compass as well. I don't think you can ever have too much memory. The extra features are not a must for geocaching, but I would spring for the Vista.

I appreciate your references to other threads on this question. While each of them covers the same general question, there are many different and interesting discussions in each thread.

I use Easygps and Expert gps with my Garmins. I had problems in the begining as well. As stated earlier, make sure you have the latest versions of software and the latest versions of firmware on your gps. Once I updated my firmware the software and gps reconized each other. You can find the firmware updates on the Garmin sight. If you can't get it to work feel free to repost. I'll be glad to help you with the details.

I often use the third north, grid. I like to use topograhic maps when serching for geocaches and hiking. Not necessary, I just enjoy maps. I navigate on the maps off of the grid north lines. I set my compass, gps to grid. That way they all match and there is no need for conversions in the field. It is really a matter of choice. If just using your gps it doesn't matter. If using compass or maps they all should match or you have to do the conversions. I recently did a multi cache where the second step was to go 325 feet south from the first step. It didn't specify, but it was magnetic south. For fun, I checked the difference for grid and true south. In the short 325 feet you could see a significant difference already. Several good threads as already stated. Several good sites on the web. Here is a great book if you are interested in directions and map stuff: Be Expert with Map and Compass by Bjön Kjellström Good question. It is good to see people posting questions of all kinds. Keep them coming! Enjoy geocaching!

Not agreeing with a post or information can be part of any discussion. Intelligent mature people can exchange information and ideas without insults. Those who result to them often have other agendas than the exchange of information. Eraseek, you have been a gentleman and have no need to be sorry. I now this is taking a risk, but here is a quote about WAAS and DGPS degradation. http://gpsinformation.net/exe/waas.html Ionospheric Corrections: "The IONO information transmitted by the WAAS system is much more accurate than the basic GPS IONO model. Also, the WAAS system will generally be more accurate than beacon based DGPS because of the way the corrections are rendered by the WAAS system and applied by the GPS receiver. The primary factor is spatial decorrelation, which is the degradation of corrections due to separation from the reference station. RTCM based DGPS corrections suffer from spatial decorrelation, but WAAS corrections do not. This Iono data (and other corrections) are constantly uploaded to the Geo Sats for re-transmission to GPS navigation receivers. There is no interpolation between ground stations by the receiver. This is because the WAAS master system computes a "grid of Iono corrections" which are location dependent based on the user's position. There is an interpolation/extrapolation process to determine the iono correction, but it is not specifically related to the location of ground stations that collect the information. The Iono-corrections grid offered by WAAS are interpolated and applied by the receiver." GPS receivers must then apply the data for corrections appropriate at their location. This may take five or ten minutes to complete in a typical receiver." It appears that this explains why distance is not a factor in WAAS corrections in the first paragraph. What do you think? "Unless I missed it, nobody in this discussion has given a reason/a basis for their belief. Probably because I suspect he’s correct, it seems to me EraSeek came the closest to giving a reason for his belief." Thank you for this concept Thot, giving a reason or basis for something. Not just labeling input as bogus or attacking the author with a false sense of superiority.

I am not assuming anything. I have merely quoted two sources, and there are others, that state that WAAS can degrade performance in some circumstances. As I have said, I had personal experience with navagation equipment while in the Navy that cost millions of dollars to install and operate. It had limitations and we often experienced system degradation in certain environments. That is part of any technology. We are talking about realtively inexpensive GPS units. WAAS is not a "holy grail." However it is a wonderful technology that will hopefully continue to improve and decrease in cost as our GPS units continue to improve and decrease in cost. We are using a technology that I use often myself. We are using a technology that is improving. However, we are using it in a way which it was not orginally designed for. Most of us are using GPS units that do not come close to the quality or design necessary to take full advantage of the WAAS signal and we are often not in an enviroment that is conducive to its use. We are often not at the end of an airprot runway. We are often not in the middle of an open agricultural field were it is used to control equipment. My brother-in-law has a large farm near Plains GA. He uses WAAS enabled GPS units there. Under these circumstances it is not illogical to assertain the possiblity this technology has limitations and may degrade performance as we use it. Attacking the sources as "boooooooooooooogus!" and "useless outdated data" is not productive and certainly serves no purpose. Yelling the word "FACT" before each statement.... Talking, intelligently about the details, such as NightPilot, Eraseek, and philthebottle is productive. Considering the sources and their time frame is helpful. Posting other sources and discusssing them is helpful. I often learn something new about WAAS from their post. I learned many things from NighPilot's post. That is the kind of post that should fill the forums. Intelligent answers and discussions. Not irrational name calling and rude responses. NightPilot, I envy your flying and especially enjoy your avatar. Thank you for your perspective and information. I trust everyone reading or particiapting in this thread will have a good day. I'm going Easter geocaching on another rainy day in central VA. I look forward to learning more.

Back from a wet soggy afternoon of geocaching in central Virginia. Yes, I had WAAS on the whole time! I was able to do a micro, regular, virtual and part of a multi. Monticello, Thomas Jefferson's home, is a great place to visit if you are ever near Charlottesville VA. At present, it has several caches in and around it. If you are ever visiting the area, let me know. I'll buy you lunch, go on a geocaching tour of your choice, and discuss interesting topics like WAAS accuracy. The area code is 22968 if you want to do a search for the area. I wonder if there are any companies that do geocaching vacations? Another topic to explore. Thank you Eraseek and philthebottle for the links. I look forward to checking them out. I appreciate your constructive input and the time you spent looking the links up.

A point well made. I know of now pilots that turn it off as they approach a landing. It is a system that was designed to be used for this. A system that works well in areas of open terrian such as airports. I also know of no pilots that rely exclusively on the technology as they land. In fact, I was amazed at its accuracy when I took a couple of introductory flying lessons. Some day I would like to take up flying as a hobby, but my wife does have her limits with my hobbies and the price of fuel! She might understand another GPS unit, but she might get upset over a plane. Your conclusion that it is illogcial that the system could not degrade performance in other conditions is where I have to disagree. Navigation tools all the way back to the discovery of the compass have had their limitations. Navigators have always used mutliple tools to verify their locations. I think WAAS is great! I use it often, but it is only a technology that has its limitations. While in the Navy I was aboard several submarines, including the USS Francis Scott Key SSBN 657. We used multiple navigation systems for navigation and weapons control. Radar, sonar, gyros, compasses, even the periscope while entering the Mediterranean Sea. Everyone new the limitations associated with each of the technologies. It would have been dangerous and illogical to believe that one technology didn't have limitations or degraded performance in certain situations. Yes America is great! However, it has its imperfections, as does WAAS. I better get going geocaching before the day is over.

For the most part, I agree with your assessment of Garmin. I do not think they are shills. I do not think they are lying. However, corporate America has often proved itself untrustworthy. In addition, I think they understand that their units do have limitations. If you read the "Warnings and Cautions" in their manuals for the hand held units you see this in CAPITAL letters, It appears Garmin realizes there are limitations to the technology as well. It appears that their lawyers want to make it clear that their handhelds have limitations to avoid lawsuits. As I said, off to go geocaching. One more question as I go, does any one have any "FACTS" from reliable up to date sources that claim their are no limitations to WAAS?

WASS is a wonderful tool. I use it often. I'm not saying don't use WAAS. Of course, it improves the accuracy of your GPS in many cases. However, like any tool, including tape measures, it has its limitations and there are multiple sources of imformation (old and new) that confirm that. If you do not take into account the limitations you can not use any tool effectively. How has WASS improved over the last few years? Are there more ground stations? Are there still not only two WAAS satellites that cover the US? Is the signal of a better quality? What about funding for GPS and WAAS satellites during the Bush administration? It is great to have a place to discuss things associated with geocaching. I appreciate those who sincerely wish to share there input in a positive manner. Because of this forum topic, I'm researching and learning much more about WAAS. A thought as I head out with my WAAS enabled GPS to go geocaching for the afternoon. I feel that everyone should consider being a premium member and help support the site that we all enjoy.

You will find in multiple discussions about WAAS that poor reception can in some cases reduce the accuracy of your GPS. Joe Mehaffey gspinformation.net In many cache locations you are obviously not out in the open. You are often in mountainous terrain and shielded by trees. Both of these situations interfere with all satellite singals, including WAAS. It appears that there are many sources of GPS information that are "boooooooooooooogus!" in your opinion.

Trimble has a free software program called Planning. It is used by surveyors who need to know when the best time is to use GPS surveying instruments. You can download it from Trimble.com. Then you will have the optimal satellite coverage time for your position.

I found this information in Geocaching for Dummies by Joel McNamara

Yes, Garmins do have an option for datums in the setup menu. It is a drop down list which includes WGS84 and NAD27. There are a few different NAD27 chocies. If you are using NAD27 you want NAD27 CONUS if you live in the contential Undited States.

What a good idea. You learn something new everyday around here!

It is important to be aware of which one your gps is set for and which one your map uses. Datums are a frame of reference for mapping. The are many differrent datums that are used around the world. As noted in a previous post, geocaching.com uses WGS84. You will also notice a link to convert to NAD27 on each cache page. Most USGS maps use NAD27. I enjoy mapping my caches before going into the field on topo maps. Try an experiment to see what a difference the two datums make. Find a cache using the correct datum and then switch to the other to see how far off you are according to your gps. I am new to geocaching as well and I have enjoyed the wealth of knowledge available here in the forums. I also recommend the book Geocaching for Dummies. Of course, there are mutiple web sights that cover the different datums. It is exciting to see someone new to geocaching. I trust you will ejoy it as you learn many new things.

My Goals for the day. 1. Find three caches. And while finding these caches... 2. Visit James Madison's plantation and learn something new about Mr. Madison. GC8001 3. Visit the village of Madison Run and find out about Atomic and Junior. GCH2TE 4. Sit by Robinson River and do some birding. GCN3XQ 5. Fix the washing machine. Needs a new timer. Part of my honey do list! Part# 661549 Looks like a nice Spring day in Virginia.