Happy #MapInfoMonday.
Today, we will play a bit with raster in MapInfo Pro again.
Sometimes you need to understand the coverage area for specific values in your raster, or an overview of how much of a place is covered by what value from your raster. For a raster with floating point data, it's hard to do as very few values will be the same. They will vary slightly but enough to not be the same. For classified raster grids, it's much easier. The Raster Statistics panel gives you an overview of the coverage per class.
Luckily, you can easily classify a floating point raster grid by specifying buckets of values that you want to group. Let me show you.
I'll be using a digital elevation model in this example. Often the data you are using here would be values you have measured and not just an elevation grid. That could be noise, air pollution, rainfall, temperature, or data captured from a wireless network. The process is the same no matter what the source of your data is.
With your input data open, select
Classify from the
Raster Operations gallery.
The Classify panel will inspect the first raster in the list and propose a way to classify it. You will often change this.
First, we want to change the intervals. Click on the
Intervals... button to open the settings for how to automatically group the values into intervals.
I want to control the grouping myself, so I will change these. I start by modifying the
Minimum and
Maximum values. In my example, I want to extract the values in intervals of 10. To do so, I change the minimum to the nearest value dividable with ten and lower than the current
Minimum Input Data Range. I do the same for the Maximum value but here it must be higher than the
Maximum Input Data Range.
I also change the
Method to
Interval Spacing and enter a value of 10. I should now end up with intervals from 20 to 80 with a spacing of 10. Click
OK to go back to the earlier panel.
Back in the initial
Classify panel, you can see that the intervals how been modified to match my settings.
I now only need to rename my classes from Class 0 to a friendlier name.
For each Class, I click inside the name and change it to a name that I want. I group my 6 classes into 3: Lower Values, Medium Values, and Higher Values. I also add the actual values for each of these classes to the name: 20-30 meters. I do this to show that you can use quite long names and also include special characters in the name. The names can be longer than 100 characters.
Once done, I hit the
Process button to create the classified raster. As you can see the
Classify operation is shown in the
Task window, and is so running in the background. While this is ongoing, you can continue using MapInfo Pro.
After a bit of time depending on the size of your raster, you will get the finished classified raster loaded into your map. My raster grid was 10 by 20 km at a resolution of 0.4 meters.
Finally, I wanted to show you where you can find the statistics about the coverage between the different classes. From the
Raster tab, click on
Raster Statistics. In the Statistics panel, click on the Chart button. You will now see the individual classes, the
Count of cells, the
Area they cover, and the
Percentage they make up of the grid.
I hope you found this useful. Stay tuned for more tips & tricks in upcoming #MapInfoMonday articles.
This post was written to give a more thorough answer to a question I got lately.
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Peter Horsbøll Møller
Principal Presales Consultant | Distinguished Engineer
Precisely | Trust in Data
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