I am trying to split the maritime boundary of India (also called as Exclusive Economic Zone, EEZ) into different polygons based on the boundary of Indian districts.
In the word file 'Conversion' attached with this post, Figure 1 contains EEZ of India and in Figure 2, I have converted the entire maritime area into different polygons, based on the border of Indian districts.
Before conversion, I tried calculating the amount of chlorophyll-a content in the Indian EEZ and the sum comes to 60,000 (approximately) for a given year. Once I converted the EEZ into different polygons, I tried calculating the chlorophyll-a content for each of these polygon, and once I sum the chl-a for all maritime district polygons as in figure 2, the total comes only to 2000.
There was a notification while doing the raster analysis that the raster file and the shape file are in different datum, when I was using the shape file as in figure 2. Then, I fixed the coordinate system so both the raster and shape files (as in figure 2) have the same projection system. I don't get the error notification anymore, but the total values of chl-a are still different, as before changing the projection system.
Moreover, once I converted the EEZ into different polygons, there are around 41 districts. When I do the raster analysis, there are only 35 districts in the output table, but the six missing districts should not create a huge difference.
Any suggestions to fix this issue will be helpful.
"Then, I fixed the coordinate system..."
How did you fix it? Project I hope rather than just defining a different coord sys.
I fixed the issue. Before, I have split the existing shape file into different polygons, while 'projecting' a different coordinate system but there was a problem which I outlined earlier. So instead, I tried creating a new shape file altogether today and this time it seemed to work properly.