Useful tools in this step: Select (), Reshape (), Add Node ()
We explored how to create a polygon in the previous blog article. Once you're created your polygon in MapInfo its very likely that you will then need to edit or amend it, luckily MapInfo makes that a very straightforward process.
Firstly, choose the polygon that you want to amend using the SELECT tool. Once you've chosen it you will then need to be able to see all of the different points that you clicked in order to make up the edge of the polygon (these are also known as nodes). So use the DRAWING tool bar to choose RESHAPE. Now that you can see all of the different individual points you can also change each of them. In the event that you actually just want to delete a point, just select the individual node with the SELECT tool and press delete on the keyboard. If you want to add a further node then the ADD NODE tool lets you do this.
Once you are happy with your polygon you can get some straightforward data on it using the 'GET INFO' option when you have right clicked using the SELECT tool. This will then show you a selection of standard information about your polygon like the boundary and area of your polygon.
This will then bring up some characteristics of this polygon as shown in the image below. One of these measurements is the total area of the polygon in squared kilometres. Notice that the great advantage of using MapInfo (or similar GIS) is that, unlike counting up squares of graph paper, any scaling adjustments required to account for the scale of the source mapping data are already automatically accounted for. MapInfo’s measurements are also very precise, which is why it is important to ensure that the digitised polygon is accurately representing the real boundaries of the contributing area.
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