Mileage in the To Reach calls

[+billwallace]

I've noticed recently that the distance/mileage given in the to reach descriptions doesn't match up to well with where I find the bench marks. Tenths to several tenths of a mile different - sometimes short and sometimes long for marks along the same route with the same starting point in the descriptions.

 

Anyone have the same experience?

 

I tried an experiment with Google Earth:

I made a path along the route described in the data sheet description.

Used the "Show Elevation Profile" feature to find the distances listed in the descriptions and made reference waypoints to help find the marks instead of keeping track of the mileage on my car.

 

Unfortunately that didn't work to well at all - for the two that I found this weekend, the reference waypoints I made were a couple of tenths off (they were at the end of a route of about 14 miles with 21 marks on it). I wasn't expecting any real degree of accuracy but I was hoping it would be closer - I was approaching these from the opposite direction from the descriptions. I'm wondering whether to scrap this idea.

 

The two marks I was referring to are

FV1182 found at N35° 21.827 W120° 12.590 and my reference point was N 35° 21.851 W 120° 12.441

FV1181 found at N35° 21.620 W120° 13.058 and my reference point was N 35° 21.685 W 120° 12.723

 

What is everyones tried-n-true method for those marks whose descriptions are simply "x miles down the road from this point and 21 feet from the road centerline" with no other landscape references?

[2oldfarts (the rockhounders)]

I've noticed recently that the distance/mileage given in the to reach descriptions doesn't match up to well with where I find the bench marks. Tenths to several tenths of a mile different - sometimes short and sometimes long for marks along the same route with the same starting point in the descriptions.

 

Anyone have the same experience?

 

I tried an experiment with Google Earth:

I made a path along the route described in the data sheet description.

Used the "Show Elevation Profile" feature to find the distances listed in the descriptions and made reference waypoints to help find the marks instead of keeping track of the mileage on my car.

 

Unfortunately that didn't work to well at all - for the two that I found this weekend, the reference waypoints I made were a couple of tenths off (they were at the end of a route of about 14 miles with 21 marks on it). I wasn't expecting any real degree of accuracy but I was hoping it would be closer - I was approaching these from the opposite direction from the descriptions. I'm wondering whether to scrap this idea.

 

The two marks I was referring to are

FV1182 found at N35° 21.827 W120° 12.590 and my reference point was N 35° 21.851 W 120° 12.441

FV1181 found at N35° 21.620 W120° 13.058 and my reference point was N 35° 21.685 W 120° 12.723

 

What is everyones tried-n-true method for those marks whose descriptions are simply "x miles down the road from this point and 21 feet from the road centerline" with no other landscape references?

 

What we have found for lines of marks, is to find a couple of the easy ones in that series and then do a mileage check on the datasheet from the given beginning point. After finding the first 1 or 2 in that series, measure from the found mark to next one in that line.

 

For instance, if the one that you found is listed as 10 miles from the library and the next one you want to find is 11.3 miles from the library, you would start at the found mark and go 1.3 miles and begin the search there. Each time start measuring from the last found mark. The actual mileage from the library does not matter it is the difference between the last found and the next one in line that matters.

 

Good luck, with the hunt.

 

John

[southpawaz]

I've used the method John describes with good success on some back-road level runs. It's especially helpful when you're hunting in the reverse direction of the described route.

 

I was just yesterday using the method you described, Bill, to try and puzzle out the location of a couple of azimuth marks, though I was using NG Topo and drawing the segments of the route rather than checking against the elevation profile.

[Bill93]

John's comments are good. Another situation you sometimes encounter is that a road has been re-routed since 1934 and the new mileage doesn't match the old one.

[AZcachemeister]

..and possibly someones odometer isn't/wasn't entirely accurate.

[+billwallace]

Thnx for the comments. I like the 'distance between marks' idea. As for odometer accuracy, I was trying to figure out a way to negate the inaccuracy of my odometer - especially after stopping and turning around and going past presumed locations to find a place to park, keeping track of all that on scratch paper was getting really messy.

[+PFF]

In my area, azimuth marks usually are beside a road. Using a protractor, draw a line outward from the main station at the described bearing. Where it crosses the described road is where the mark will be. You can use the pointer in Google Maps or Google Earth to get the Lat/Long. Enter the position into your GPS receiver, and you won't have to worry about the odometer.

 

If you pay attention to which side of the road is mentioned in the description, you'll be amazed at how close the GPS will get you!

 

-Paul-

[Z15]

John's comments are good. Another situation you sometimes encounter is that a road has been re-routed since 1934 and the new mileage doesn't match the old one.

Not only rerouted but it could be in the same location but the hills and curves may have been flattened and thus the mileage would get shorter or longer. Having worked for the DOT and having access to plans and ROW maps I have seen this many times. For instance; one road in my area is completely different from its 1948 location but in the same general location and the junction used in 1948 was moved 1/2 mile farther along the intersection route. If you did not have old maps or plans you might not be able to tell from out in the field as things changed in 1955. Even the USGS could not locate some marks because instead of 3.5 miles they would now 3.2 miles, instead of 60 ft from C/L as in 1948 it was now 160 ft from the existing C/L.

 

You have to put yourself in past and using Google maps or anything on the computer is often not accurate to the extent you expect it to be. You are better off using paper USGS maps. We use to use Delorme Topo quads loaded into my laptop plugged into a differential Garmin GPS and I often found the plotted location on the computer map to be completely off the location on the ground. The location on the map screen (software) would place the mark on low ground when you new it was 1/8th miles away on the hill where the map screen showed a triangle. Most of the time the computer maps are only accurate to a certain magnification and if you zoom in it goes all out of wack.

Edited March 27, 2011 by Z15

[+billwallace]

John's comments are good. Another situation you sometimes encounter is that a road has been re-routed since 1934 and the new mileage doesn't match the old one.

Not only rerouted but it could be in the same location but the hills and curves may have been flattened and thus the mileage would get shorter or longer. Having worked for the DOT and having access to plans and ROW maps I have seen this many times. For instance; one road in my area is completely different from its 1948 location but in the same general location and the junction used in 1948 was moved 1/2 mile farther along the intersection route. If you did not have old maps or plans you might not be able to tell from out in the field as things changed in 1955. Even the USGS could not locate some marks because instead of 3.5 miles they would now 3.2 miles, instead of 60 ft from C/L as in 1948 it was now 160 ft from the existing C/L.

 

You have to put yourself in past and using Google maps or anything on the computer is often not accurate to the extent you expect it to be. You are better off using paper USGS maps. We use to use Delorme Topo quads loaded into my laptop plugged into a differential Garmin GPS and I often found the plotted location on the computer map to be completely off the location on the ground. The location on the map screen (software) would place the mark on low ground when you new it was 1/8th miles away on the hill where the map screen showed a triangle. Most of the time the computer maps are only accurate to a certain magnification and if you zoom in it goes all out of wack.

hmmmm.... thnx

 

now i just need to get a day off

[+Harry Dolphin]

Thnx for the comments. I like the 'distance between marks' idea. As for odometer accuracy, I was trying to figure out a way to negate the inaccuracy of my odometer - especially after stopping and turning around and going past presumed locations to find a place to park, keeping track of all that on scratch paper was getting really messy.

 

I went looking for one listed aas '1.00 mile from the intersecton of Harford St and Pennsylvania Ave'. I marked it on my GPS. When I got to the listed coords, I used the GPS to track back to the intersection. (Go To on road.) 300' down the road I found the retention basin. (I would call it a storm sewer. Which is what confused me and another benchmarker.) I think I found it, but the ground was too frozen to dig. Oh, well. I'll be back.