I have a polygon shapefile with an area of about 1400 sq. km. But it is being calculated in the attribute table as only 0.1272 sq. m. What's the problem here?
You coordinate system is most likely a Geographic Coordinate system (i.e. WGS_84). You can reproject your data to a Projected Coordinate System, or change the data frame to a Projected Coordinate System. When you calculate area, you can specify the coordinate system of the data frame.
Calculating area, length, and other geometric properties—Help | ArcGIS for Desktop
Thanks for the reply Jake.
Actually reprojecting the shapefile was the first thing I did after adding it to the window. I reprojected it to WGS 1984 UTM 43N. It was after this process that I went for the area calculation.
Another thing I'd like to add is that after posting this question, I redownloaded the shapefile.zip from the internet source and I ran the area calculation function for it and I don't understand how or why but I got the right result.
So basically I've two same shapelfiles, an old one and a new one, but I'm getting different areas for them one right and one wrong.
Right = 1427.58 sq. km
Wrong = 0.1272 sq. m
Can you zip and upload the shapfile to this thread?
I can but I don't see any option for posting it???
Click on Use advaced editor at the top right when replying:
You should then see an option at the bottom left to attach a file:
From one problem to another . . . There's no option for "use advanced editor" either.
I went through the internet in search of a solution and apparently I found 2, none of them worked for me though.
1. Reprojecting the shapefile, which I already did but it didn't work.
2. Using the dissolve tool to merge all the polygons in the shapefile to get one area for all of the shapefile. The problem here is that there are no other polygons in the shapefile except for the polygon shapefile itself, at least there are none visually. But then I thought my shapefile might be a cluster of lot of smaller polygon shapefiles that are not visual and the area that is being calculated (0.1272 sq. m) is the area of one such polygon (which I doubt as it's too small) so I ran the dissolve tool just to be sure and then calculated the area but it didn't work out even then and I got the same area.
Can you show us the extents of the "wrong" one. I still think that Jake is correct and there is something wrong with the coord sys definition with that one.
I have added the images to the thread
the 1st two are the wrong ones
Look at those left & right values. Your polygon is <50cm across.
That doesn't sound right at all.
So, I would conclude that those numbers are degrees, not metres at all. That feature is not in UTM.
So I reprojected it again but I got the same results. My old and new shapefile both have the same properties but they yield different results. On top of that, the old shapefile used to give the correct result before. I didn't use it for a few days and then this error started occuring.
copy the shapefiles to a new folder.
use windows explorer and delete the *.prj file
Open arcmap, add the shapefile to an empty dataframe... absolutely no other data.
Zoom to your shapefile and examine the coordinates … are they in the range -180 to 180 W to E and 90 to -90 N to S?
Then you have a geographic coordinate system
As a check, calculate the centroid of the polygon... don't set anything, let it calculate the units as they are... are they like above? Then you have a geographic coordinate system
Now... if the numbers in either of those two scenarios yield big numbers, then you are working with a projected coordinate system.
But... just because you have a *.prj file doesn't make it correct... they get Defined (projection) incorrectly all the time.
You just need to use the Define Projection tool to define it correctly first THEN you can use the Project tool
Retrieving data ...