Reading map coordinates

During yesterday’s lab we used the latitude/longitude ruler and UTM grid tool from Map Tools to find the coordinates of different features on the topographic maps. There are several ways you can improve the accuracy of your meaurements.

First, make sure the lines you drew on the map line up with the tick marks on the side of the map. The UTM ticks are inclined a bit from the main axis on the map (remember grid north) and it’s easy to get them off center. Strictly speaking you don’t need to draw lines on the map. You can get by with a long ruler in a pinch.

Know what the precision to which you are measuring. For example, the UTM grid is designed to read to 100 meter precision. Your answer should reflect that. With UTM we always read over and up, easting and northing.

The Lat/Long ruler has a 0.01minute side and a second side. Make sure you use the right one. since Longitudes increase from east to west in the western hemisphere we place the zero mark on the east guide line. I find it helps to frequently check that the zero and the 2.5 mark are lined up properly as I slide the ruler up and down the meridians.

Can anyone come up with other tips?

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