SIY5.TXT Topographic Maps and Aerial Photographs 29 Chapter 5 Topographic Maps and Aerial Photographs The first survey which you should do on any piece of land is to simply to look at the topographic map. Topo maps at a scale of 2000 feet per inch are available for most of the United States for less than five bux [$5] delivered. See USGS or Timely Discount Topos in Chapter 14 for instructions on where to order a topo map in the USA. In other parts of the world, write the Geological Survey in your capital. Having taught topo map reading at the University of Kentucky, I know that I cannot teach you to read a topo map by mail. The only way for you to learn to read topo maps is to compare a topo map and the real ground. Order the topo map for a familiar area, like around your home. Be sure that you get the pamphlet "Topographic Map Symbols" too. Then walk around with the map, compass, and symbol sheet. Orient the map so that the North Arrow points the same way as the compass needle. Compare the map with reality. The only really different feature of the topo map is the topographic contour lines, those random brown squiggles doodled all over the map. If these contour lines still seem like random brown squiggles to you, try this. Imagine the Second Great Flood. As The Sea rises, the new shoreline will move up into the land. At any given rise in The Sea level above today's Mean Sea Level (MSL), the new shoreline will be represented by the contour line at that level. You can see [hopefully] that in level land, a large area will be flooded by a small rise in The Sea. On steep ground, the new land flooded would be only a narrow strip. Bays will reach up into the valleys, and ridges will extend out into The Sea. High ground will eventually become a chain of islands. The contour lines do all these things, without the necessity of all that water. Be sure to ask for the free pamphlet "Topographic Map Symbols" when you order your first topos. Every house, barn, creek, river, rapids, dam, highway, road, jeeptrail, government boundary, school, cemetery, church, pond, lake, picnic grounds, railroad, high tension line, pipeline, mine, stripmine, woodlot, swamp, spring, windmill, &c, etc, et cetera is marked with a special symbol. In Township and Range country, the section corners and lines are marked. Sometimes fencelines are on the map too. Once you have learned to read a topo map on familiar ground, you can read a map of any place of interest. Map Reference Libraries are located at most college Geology and Geography Departments, and at major city libraries. The addresses of these Map Reference Libraries are listed on the Index Map for that state. SIY5.TXT Topographic Maps and Aerial Photographs 30 Many public libraries have topographic maps of the local area. Topos are so quick and cheap from Timely Discount Topos that you can order them for an area of interest and then use them for impressive wallpaper. Each state has an index map or a "green book" which you can use to determine the proper map to order. Each topo covers about 7 miles across for the standard 7.5 minute map. It is named for some prominent feature, generally the largest city, village, or hamlet, but sometimes for some other landmark. Each map tells which maps join on the sides and corners. You can make three guesses of the proper map and get the index map or "green book" and a "Topographic Map Symbols" pamphlet all for less than ten bux [$10] delivered. This will make you an instant expert on local land use. Aerial photographs for agricultural areas are available in your county ASCS office. See Chapter 14. Visit them with the area of interest marked on your topo map. Use the office photo mosaic index to locate the aerial photo covering your land. It may help if you know the name of a nearby farmer so that the clerk can look up the photo of his farm. County ASCS offices usually have photos of all agricultural land at a scale of 660 or 1000 feet per inch. Fields, trees, buildings, roads, cowpaths, streams, fences, etc., etc. can be easily seen on the photos. ASCS may have their version of the property boundaries and ownership marked on the photos. Where the property boundaries are field boundaries, the ASCS version is usually quite accurate. In woodland, they are guaranteed incorrect. You may also be interested in using a stereoscope. With this instrument, two aerial photos are combined to create a 3-D image of the land. This is one of those things which you just must see to believe! In non agricultural areas, the BLM, National Forest, Corpse [sick] of Engineers, or other agency may have aerial photography. Sometimes in color. I doubt that there is any part of the United States for which aerial photography is not available. I can't teach you to read topo maps or aerial photos by mail. But if you have trouble finding the proper item, I might be able to help. And if you have any interesting scientific or engineering applications, I'd be glad to consult. Agriculture, geology, hydrology, botany, forestry, wildlife management, archaeology, land use planning, flood management, historical research, construction engineering, and law enforcement come quickly to mind. SIY5.TXT Topographic Maps and Aerial Photographs 31 The Silva Ranger is especially handy for determining your location on a topo map. First, find some recognizable landmark both on the ground and on the map. Then measure the direction to it with the Ranger. Next, place the Ranger on the map with the edge passing thru your landmark and the meridian lines inside of the compass dial aligned with the north-south lines on your topo map. Your location is along this line. If you shoot and plot the direction to another landmark, your location will be where the two plotted lines cross. You can get a feel for the amount of error involved by plotting directions from several landmarks. With the Ranger this is so fast and easy that it can be easier done than said, once you find your landmark. If you have ever tried this with a Brunton pocket transit, protractor, ruler, and pencil, then you will really appreciate having everything in one instrument and the protractor already set to the proper reading too. Geologists' Heaven! Dave Beiter CAVE Inc 1/2 Fast Road Ritner KY 42639 606/376-3137