Would you like to...

Print this page

Email this page

Post a comment

User Opinions

83% 16%

---

How would you rate this answer?

Helpful

Not helpful

Thank you for rating this answer.

When you display maps based on latitude, longitude coordinates extending over a large region, they might appear somewhat distorted. This occurs because one degree of latitude is not equivalent to one degree of longitude. For example, consider a base map of the state of California (CA.GSB).

To determine the scaling factors:

1. Determine the latitude for the parallel through the center of the map, and obtain the cosine for this latitude value. The center parallel in CA.GSB is approximately 37.27 degrees. The cosine of 37.27 is 0.80.

2. Select Map in the Object Manager to open the map properties in the Property Manager.

3. Go to the Scale tab and set the X scale for the map. You can set either the Length value or the Map units per in. value. For this example, the X scale in map units is 1.72.

4. Uncheck the Proportional XY scaling check box.

5. Multiply the X scale Map units per in. value by the cosine of the latitude, and enter this number into the Y scale Map units per in. field. 1.72 (X scale Map units per in) x 0.80 (cosine of latitude) = 1.38 (Y scale Map units per in)

6. Click OK and the map is drawn with the new scaling. 

For example, please see attached Surfer 10 SRF file which shows the map unscaled (left) and also scaled according to the cosine of the latitude (right).