Downloading Topo Maps, Air Photos and Making Stereo Pairs.

• I decided to make a color topo detail and some stereo pairs for Antelope Ridge in Wyoming.

• Since you always need these before you go to the field, here is a step-by-step description of how I did it.

• Prof. Smart

Antelope Ridge, Fremont Co., Wyoming43 34' 10.36" 108 57' 17.09"43.569ºN, 108.955ºW

43.57880 -108.98430

I searched google for the latitude and longitude, then copied the coordinates (note my highlight below) onto a text file, which I print out.

Then I visited the first entry, the lat - long.com web site.

http://www.trails.com/topo.aspx?lat=43.5694&lon=-108.95485&s=50&size=s&style=drgsr

It's powered by Google, with nice color. Antelope Ridge has the red balloon.

Notice the blue marker bed. The central area looks like a complex series of plunging anticlines and synclines

1. I zoomed in. Look at those dips: this area to the SE is a syncline, plunging SE

The ridge has steeply dipping beds, but I can't see the limbs of the fold well. Let me get a terrain sheet, and some stereo pairs

Beds on the north limb are dipping away from the ridge

http://www.mytopo.com/maps/index.cfm?mtlat=43.57880&mtlon=-108.98430

http://www.mytopo.com/maps/index.cfm?mtlat=43.57880&mtlon=-108.98430

Most Terraserver and Google Earth air photos don’t overlap, they are mosaics. You can't get stereo pairs from them. Go to Earth Explorer

http://earthexplorer.usgs.gov/ and enter the lat/lon

Click Data Sets

Click Decimal

Click Add Coordinate Click Add

Go to the left side of the Earth Explorer page. Click Aerial Photography, and select NAPP

And click Results

These two look like a pair, same latitude

You have to be patient. I have a pop-up blocker, so have to crtl -click at times.

This is what you get. I use a screen grabber to save it.

Get a pair of adjacent photos.I used the Windows 7 Snipping Tool

Notice how overlapping objects are aligned.

The rest is trial and error, put them side-by-side, correct way around **,print them out, and see if each object is separated by about the distance between your eyes. Try the printout ("Current Slide") with your stereoscope. If too close or too far apart, hit Edit, Select All, and change the size with a CORNER button to keep the aspect ratio.

Here's the South end of Antelope Ridge, with plenty of dipping strata to give you the structure.

** If you don't, ridges will look like valleys.

Here is the nearby dome-like structure, with lots of faults.

These tools permit a lot of valuable preparation before you leave for your

field season.