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Using "tie points" in rasters [message #93199]

Wed, 11 May 2016 14:35

GB
Messages: 2
Registered: May 2016

Junior Member

Hello,

I am working with a digital elevation map raster and ran into a problem that I am unsure how to approach.

Once I get the spatial reference object of my DEM raster, I then get the tie_point_pixel, the tie_point_map, and pixel_size from the spatialref. I then seek to transform the map coordinates of a set of LiDAR points into the pixel indices of my raster. The thing I am confused about is how rounding plays into this problem.

For instance, lets say that I use the following function to convert the x-coordinate of my lidar point into pixel coordinates:
(lidar_point_x-tie_point_map[0])/pixel_size[0]
But, I get a decimal place in the outcome. Lets say that the decimal point is 0.64. Would this decimal point translate into the point belonging to index 0 or to index 1?

I suppose I am confused about if the tie_point_map is centered on the tie_point_pixel such that it extends a range of -0.5*pixel_size to 0.5*pixel_size. If anyone could elaborate on this I would be very thankful.

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[Message index]

		Using "tie points" in rasters By: GB on Wed, 11 May 2016 14:35
		Re: Using "tie points" in rasters By: jiashenyue on Wed, 11 May 2016 20:21
		Re: Using "tie points" in rasters By: GB on Thu, 12 May 2016 05:52

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