Katie Riley
Summary of the Trend of Area Distortion as Latitude Increases in
Each of the Four Projections
Robinson:
Area distortion increases as absolute latitude increases. In the Tissot_Robinson the average area
for at the equator is approximately 10.5 million sq km. At +/- 30 degrees latitude the area is
slightly larger at 11.7 million sq km and at +/- 60 it is even larger at 15.2 million sq km. So the
average area of the indicatrices becomes larger the area distortion.
Mercator:
Area distortion increases as absolute latitude increases as well. At the equator the average area at
1.3 million sq km. By +/- 30 degrees latitude the area of the indicatrices is about 1.7 million sq
km and by +/- 60 degrees latitude the area of the indicatrices is about 5.2 million sq km. As you
can see the area distortions increases with latitude and the distortion is greater than that of the
Robinson projection.
Bonne Projection:
The area distortion for this projection is very low compared to the other projections. Around the
equator the average area for the indicatrices is around 128,944 sq km. At +/- 30 degrees latitude
the area of the indicatrices only differs by about 200 sq km and at +/- 60 degrees latitude the area
only differs from +/- 30 by 400 sq km. So the area distortion slightly increases with latitude, but
so far has the least area distortion of the four projections.
Orthographic:
The area distortion does not seem to have a direction correlation with change in latitude. The
area of the indicatrices differ greatly even at the equator different identification points have
different average areas. There is an area of 0 km sq at several points at the equator and then again
at – 60 degrees latitude is also zero km sq, and yet at +60 degrees latitude the area is
approximately 745,000 km sq. So overall I can see no direct relationship between latitude,
count_LAT, or OID and average area of the indicatrices.