Image Tips in ArcMap


So you’ve loaded your image into ArcMap and the image displays incorrect colour or there is no data values around the outside of the image that is masking crucial features in your map. How can you quick rectify these annoyances? Well this is where the Image Analysis  window comes in handy.

Introduced in ArcMap 10.1 the  Image Analysis Window is accessed from the Display menu in ArcMap . The Image Analysis window supports the analysis and exploitation of image and raster data in ArcMap, with a collection of commonly used display capabilities, processes, and measurement tools. Essentially all your image needs in one place.

The Windows is dived in 5 key areas Layer List, Display, Processing, Options and Mensuration.

So let’s address the issue of NODATA mentioned above. In order to perform and operation on an image it is first necessary to select the image in the Layer List. Next select the Background check box in the Display section.  It sets all the background values to 0 and makes them transparent. Easy! You don’t even need to access the properties of the image.

Talking of the properties have you noticed that sometime when you zoom into an image the region appears dark compared to the rest of the image, but you would really like to enhance it. Well it is as simple as selecting the DRA checkbox. DRA is short for Dynamic Range Adjustment.  It adjusts the stretch applied to the selected raster layer using only the data contained within the data frame extent, so providing the optimal display for the area on the screen. Each time you zoom or pan it recalculated the display.

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So what about that image that seems to take for ever to draw and each time you pan it has to redraw. Well there is a tool on the in the Window called Accelerate. Simply select the image you want to speed up in the Layer List, right click and select Accelerate. Your image is now loaded to the graphics card and will display very fast. Try panning zooming you’ll be impressed.

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Finally, some image processing.  There are some really great tools here which are quick to access and quick to process as they are all done in memory for only the area on the screen. Select an image, or multiple images in the Layer List and depending on what you have selected items will become active in the processing area of the form. For example the NDVI tool is active when you you have an image selected with a RED and NEAR INFRA RED bands. Or the Pan Sharpening tool is highlighted when you have an RGB and Panchromatic image selected. Or if you have three grey scale images selected the Band Stack tool becomes available.

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It is as easy as select the image and pressing the button. Each result is added to the Layer List but is Temporary. To Save your results simple select the result in the Layer List and select the Save tool.

Explore the Image Analysis tool further to enhance you image workflows

Happy image processing

Gordon

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