Geocaching for survey pins and markers

We recently went out to take some pics of a fairly large parcel east of Sierra Army Depot. It is 160 acres between the eastern depot boundary and Duck Lake. So how does one go about locating the property on a map? You need a parcel map that shows the Township and Range information. In this example we are working on parcel 10 in the northwest corner of Section 21, Township 27 North and Range 17 East. Ok so how do I get that information loaded into my GPS? There are probably a few ways but I use a software program called Terrain Navigator Pro. It was originally owned by Maptech.com but now is under mytopo.com.

There aren’t any footages on this map but there are 640 acres in a Section and one Section is conveniently one square mile. 640 divided by four is 160. So this makes it easy to measure in the software. We don’t get the exact angle like we would in a surveyors map like 89.01 degrees but we can follow the township and range lines where possible and use the cardinal points of the compass to get us back to the starting point.

In our example the northwest corner of the northwest parcel, the corner with Sections 16,17 & 20 is where I start using routes and waypoints in the software. The distance in this example is east 2640 feet, south 2640 feet, west 2640 feet, then back north 2640 feet and toggle the route closed in software.

There is a learning curve to any new software and there’s a lot to learn about with TNP as well. One of the nice features of TNP is that with your paid annual subscription you get satellite views as well.

One important thing to remember is that you will need to set your GPS with the same DATUM as the map you are using. There might be small errors in your GPS coordinates but you will probably be closer than you might think. Our Range and Township maps use the North American 1927 Datum. In your GPS you will need to change your Datum to NAD27.
Due to copy write laws I’m not going to copy and paste what Garmin says but here is a link for what a DATUM is: http://www8.garmin.com/support/faqs/faq.jsp?faq=17

In my old Garmin Etrex Legend you change it by going to the main menu>setup>units>map datum and then scroll through all the choices until you see NAD27 and select it. Write down what your GPS is currently set at so you can change it back later if needed. WGS84 is the default datum in the older Garmin GPS units like ours.

The GPS unit we have came with a serial data cable but the newer ones use a USB connector and are much faster. You can upload and download any route, waypoint and track and the software lets you select which ones to load.

We were surprised when we found a well on the property and a cistern. Later it was found in the county records that there was a permit pulled for a well in 1990. That’s the same date we saw etched into the cement on the edge of the cistern. I “MARKED” the location in my GPS and named it “WELL” so I’d know what it was if I marked a lot of waypoints there.

When we returned I uploaded the waypoint to my software and could see it was clearly within the boundary of the property.

DUCK LAKE 160 ac. note the well

Cistern at the well

Using a GPS is not hard and using old topo maps you can see many interesting places to search out. I mainly use the Garmin for this kind of work but have a few others as well. One for the car and one for flying but we haven’t used that one in a while. If you have any questions or comments I’d be happy to respond.

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One Response to “Geocaching for survey pins and markers”

  1. Golf GPS Units on June 22, 2010 at 11:18 pm

    Excellent job.