Merging and Cropping *.asc data

[ShaunWasik]

Hello All,

New user of ArcGIS and new member of the forum!

I am trying to make use of LIDAR data received from the EA as part of an assignment for university.  The data is originally in asc format.

My ultimate aim is to create a Raster file which is cropped at the extents on my proposed site.  The site is at the intersection of four 1km grids and I have no idea how to firstly combine these data sets, then crop them to the site.

One method I have tried is to convert each file into a simple CSV file, then digitise the point data.  This works fine, and I end up with 4 point data layers, but I don't know how to stick them together!

Would anyone be able to provide some advise on this problem?

Thank you in advance for your help.

Wizzo

[JoshuaChisholm]

Hello Wizzo,

Does the merge tool suit you needs?

Once you have one point feature class you'll want to interpolate it into a grid. There are a ton of interpolation tools (Toolboxes > Geostatistical Analyst Tools > Interpolation). There is no best tool and you'll be able to find a ton of academic papers comparing the different methods. That being said, a lot of the discussion is based on how to predict a value in between two points (where you have no data). Since you are working with LiDAR, you probably have a very dense set of points (multiple points per m²). This means it should actually matter much which interpolation tool you use.

If your data is dense enough (and has no breaks/missing areas), you should look into the Points to Raster tool as well. This tool will just produce a grid and use the points to get a value for all the cells. If there are no points in a cell, the cell will not be created. This could mean holes in your grid if there are areas missing in your LiDAR data (lakes can have lower return rates).

Let me know how it goes!

[ShaunWasik]

Hi hua17,

Thank you very much for your help.  Worked a treat!

Wizzo