ARCMAP-PIXEL CENTER

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10-26-2015 07:46 AM
ChuckTurlington
Occasional Contributor II

Hello,

I am using ArcMap 10.2.1.

Is there a way to identify an aerial raster pixel cell or locate the center of each pixel?

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PeterBecker
Esri Regular Contributor

I'm not 100% sure what you are asking.

If you are trying to identify the the alignment of the pixels, then best is to look at the properties of the raster, which will return the Extent (Top,Left,Right,Bottom) and the cell size. Assuming that the imagery is only georeferneced with a simple scale and shift transform then the coordinates of all pixel centers can be easily computed. IE Col Center = Left + (Cellsize * (N+0.5) ) , Row = Top - (Cellsize * (N+0.5) )

If you are looking to visually identify the extents of each pixel then there are two methods.

a) Change the layer display resamapling to Nearest Neighbor and you will see the edges of the pixel clearly when you zoom in.

b) Open Pixel Inspector  (Right click on Menu area, Customize, Commands, Raster, Pixel Inspector)

This will draw a grid around the pixels as well as show you a grid of the actual values.

PixelInspector.jpg

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3 Replies
LukeSturtevant
Occasional Contributor III

Well I'm not sure about getting a specific pixel cell center, but have you tried Raster To Point​? This will unfortunately take a long time because it gives you a point at every cell center in your raster image. I suppose you could do an Extract By Attribute​ if your raster is an integer raster and the cells you are interested in have a specific value.

CodyBenkelman
Esri Regular Contributor

Chuck

Can you explain more fully what data you have, how it's been processed, and what you are seeking to do?  If you have a raw aerial image and you're trying to orthorectify it and properly place each pixel into earth coordinates, that is vastly different than if you have an orthophoto and you're simply seeking to identify the locations of the pixels.

If you are seeking to identify sample points with subpixel precision, It is worth noting that the data format can have an impact and must be carefully reviewed.  For a specific example, the GeoTIFF spec includes a tag for "pixel_is_point" vs. "pixel_is_area" that must be set properly depending on how the data was captured, and how it was processed.  Given an example image, if you change from one setting to the other, your image will shift 1/2 pixel in both X and Y, indicating that the pixel value either represents a sample taken at the center of a pixel, or alternatively at the upper left corner (the intersection of 4 pixels). 

I don't recall off the top of my head which setting means which case, so if this is pertinent to your question, we'd have to dig deeper - but if my comment is off topic, then when you clarify your objectives perhaps we can advise better.

Cody B.

PeterBecker
Esri Regular Contributor

I'm not 100% sure what you are asking.

If you are trying to identify the the alignment of the pixels, then best is to look at the properties of the raster, which will return the Extent (Top,Left,Right,Bottom) and the cell size. Assuming that the imagery is only georeferneced with a simple scale and shift transform then the coordinates of all pixel centers can be easily computed. IE Col Center = Left + (Cellsize * (N+0.5) ) , Row = Top - (Cellsize * (N+0.5) )

If you are looking to visually identify the extents of each pixel then there are two methods.

a) Change the layer display resamapling to Nearest Neighbor and you will see the edges of the pixel clearly when you zoom in.

b) Open Pixel Inspector  (Right click on Menu area, Customize, Commands, Raster, Pixel Inspector)

This will draw a grid around the pixels as well as show you a grid of the actual values.

PixelInspector.jpg