topic Re: Elevation issue with .asc files in ArcGIS Pro Questions

Elevation issue with .asc files

KevinDodd — Sat, 29 Jan 2022 12:15:03 GMT

Hello, first time positing so I hope this is the correct place.

I have received multiple .asc files (Lidar Data) that I would like to create a surface from in Civil3D Autocad. However, when I load in the file it looks like the height values are in millimetres. Do .asc files from ArcGIS always have heights in millimetres or can they be exported with heights in metres?

Thanks in advance.

Re: Elevation issue with .asc files

DanPatterson — Sat, 29 Jan 2022 14:03:53 GMT

Were you using the export raster approach? was scaling checked on or off

Export or convert raster datasets—ArcGIS Pro | Documentation

Raster to ASCII (Conversion)—ArcGIS Pro | Documentation

or Copy Raster?

I am not sure but it is a great way to produce an elevation surface in integer form since the decimal is removed. It retains the precision yet would reduce the file size when saved. All you need to do if you would prefer a floating point raster is do the division (aka, by 1000) and if you forgot, it would be pretty obvious that the elevations don't represent meters.

Re: Elevation issue with .asc files

KevinDodd — Sat, 29 Jan 2022 14:17:12 GMT

Hello Dan,

Thank you for the reply. Unfortunately I don't know how the files were generated. I received the files from a client who purchased the data set from a third party.

What you have said about reducing the file size is interesting. The file sizes are around 25MB and cover an area of 1km².

Do you know of a straight forward way to covert the file to a floating point raster?

Thanks again for the reply.

Re: Elevation issue with .asc files

KevinDodd — Sat, 29 Jan 2022 18:01:56 GMT

Hello Dan, thank you for the reply.

I received the data from a client who was given it by a third party so I am not sure how it was exported.

Do you know of an easy way to covert the files to a floating point raster?

Re: Elevation issue with .asc files

DanPatterson — Sat, 29 Jan 2022 19:08:31 GMT

hmmmm the short answer woud be

raster * 1.0

or in your case multiply by 0.001

to convert millimeters into meters