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While we are estimating the elevation of a location, we want to get as close as possible. If the location for which you need to know the elevation is not on a contour line, you want to furtherestimate its elevation.

For example, if the point looks like it is halfway between two contour lines, then add (or subtract) half the contour interval. If the point looks like it is a third or three-quarters of the way between two lines then add or subtract a third or three-quarters of the contour interval, respectively. If the point is on top of a hill (surrounded by a closed contour), then take half the contour interval for the final elevation.

Let's try it out.

   
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ANSWER: 630 feet. Note that the silo is enclosed in an oddly shaped contour that closes. Therefore, it is at the top of the hill. You should see the 600 ft. index contour and note that there is only one contour line between the silo and the index contour, so the elevation is at least 620 ft. However, it is not touching the contour line so it can't be 620. There is also no other contour line near the silo other than the 620. So since it doens't touch the 620 ft. contour and you have determined it is at the top of a hill (closed contour shows this), then you take half the contour interval (10 ft), add it to 620 and get 630 feet.
       
                                           
                                         
                                           
     

ANSWER: 7,060 feet. First, you must determine the contour interval, which is 40 feet. To determine the contour interval, find two index contours, in this case you can use 7,000 and 7,200. Note that there are four lines between them, with an index contour being the fifth line. Divide 200 (derived from 7,200-7,000) by 5 and you get 40 feet. That is your contour interval. If you missed this, then you need to go to Step 2 and practice a little more.

Next, notice that the Red X is between the 7,040 ft and 7,080 contour and it looks like it is approximately halfway between the contours. This being the case, add half the contour interval to 7,040 and you get 7,060 feet.

     
                                           
                                         
                                           
   
ANSWER: 8,420 feet. The most important item to notice is that the 8,400 contour surrounds the Red X. Also notice that the Red X is approximately halfway in between the lines. You can also tell you are going uphill by looking at the index contour just below the 8,400; it is 8,200. Therefore, you take half the contour interval of 40, which is 20 and add it to 8,400 and get an elevation of 8,420 feet.
         
                                           
                                         
                                           
       
ANSWER: Approximately 8,213. Notice that the Red X is between the 8,200 index contour and the 8,240 contour. Next, estimate it's distance; it isn't halfway but probably more than a fourth. An education guess (which are are now entitled to make, would be about a third. One third of 40 feet (which is the contour interval) is approximately 13 feet, so therefore 8,213 feet in elevation.
           
   
 
So, you have made it this far. If you think you need a little more work, then click on one of the buttons below for a little refresher. Otherwise, select the "Final Review" button and go to the review, which you should read prior to taking the final practice test.
GOOD LUCK!
 
   
       
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Last update: 10/30/03