2

I am VERY new to ArcMap and GIS in general.

I converted some lidar data to a GEOTIFF, using a program called CARIS (it was an .csar file) and imported this into ArcMap. There are some areas that are showing up as black (0,0,0).

Is there a way to modify these pixels to match the surrounding data, or interpolate them?

Ultimately, I will want to convert this over to a ASCII file to input into a Flow 3D program. (I will probably be asking future questions about that too!)

Am I on the right path?

Or is there an easier way to go about this?

enter image description here

1

You could use this approach Changing a color-mapped raster layer to use the RGB renderer

If your raster has a color map, it is displayed with the Colormap rendered by default. You can change this to use the RGB renderer.

  • Click the Add Data button Add Data to add a raster to ArcMap.
  • Click Windows on the Main menu to view the Image Analysis window, and click * * Image Analysis.
  • Click the raster layer in the Image Analysis window.
  • Click the Colormap to RGB button Colormap To RGB in the Processing section of the window.
  • This adds a temporary raster dataset layer to the table of contents.
  • It does not allow me to select that button. Does that mean I am not able to modify it?[![enter image description here][1]][1] [1]: i.stack.imgur.com/gXQqE.jpg – Chad Sep 11 '17 at 17:06
  • That is possible, make sure you don't have a lock on the image file. – whyzar Sep 11 '17 at 17:07
1

You are seeing this effect because LiDAR doesn't like water, it acts like a mirror, in the centre of a run (flight) the intensity is very high but just outside centre the pulse is reflected away (angle of incidence = angle of reflection) and does not return to the sensor and therefore records no return. You can interpolate with a terrain, provided you have 3d analyst extension available or with a LAS dataset (basic license requires 3d or spatial analyst).

Interpolating will close in gaps between valid records - ALL gaps up to a boundary called a convex hull, even over the land. You could make a terrain or LAS dataset from all your records restricted to ASPRS class 2, 8 and 9 (Ground, Model Key and Water), convert to raster and then Extract by Attributes to restrict to elevations below your intended area.

To import your LAS for a terrain use LAS to MultiPoint which is far more efficient than creating single points for each pulse/return. (3d analyst required)

To export a terrain to a raster you will need 3d analyst regardless of license level, use the tool Terrain to Raster. Linear interpolation method is faster but can look blocky, Natural Neighbors is slower but creates a smoother raster.

To export a LiDAR (LAS) dataset to raster use the LAS Dataset to Raster tool which will offer more interpolation methods but as you want to fill in the blanks stick with Natural Neighbors or Linear fill method.

If you are on a basic license with no 3d or spatial analyst extension you can look at LASTools as a viable alternative, there's a GUI available in QGIS. Licensing isn't too expensive and the tools are efficient; Or contact your local Esri representative to obtain extension(s) or upgrade your license.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.