Processing ascii raster image LIDAR files success

[andyf]

This is something I've just done for someone over on the HB forums however hopefully it'll help here for those who don't have full on proper LIDAR data, especially in parts of the UK where the only data available is in ascii format due to the information on the Environment Agency website.

The process I used involved using LASTools and also ArcGIS Pro although I'm pretty certain it can be completed without the last part (especially as I've only got 8 days left on my free trial!!!)

If you download the ascii raster images from the environment agency website (listed as a composite dsm or dtm file) you can then use the LASTools txt2las convertor to change the files to *.las files. These however don't work straight away with Chad's tool as the LIDAR data is unclassified. This is where ArcGIS pro is used to convert the las files to classified datasets and then processing those in Chad's tool have yielded a workable file that appears to be correct and match up with the OSM data... see below for my first attempt for Bishop Auckland golf club in the UK.

So in short, this is using raster ascii files rather than full on LIDAR las files but it does seem to give us a workaround should we need it.
I'm going to see if I can use the LASTools classify feature in order to avoid the need for ArcGIS Pro and then hopefully we will have a free way of doing it.

Andy

[paddyjk19]

Amazing stuff! Thanks for doing this

[paddyjk19]

Nov 25, 2019 14:49:49 GMT -5 andyf said:

This is something I've just done for someone over on the HB forums however hopefully it'll help here for those who don't have full on proper LIDAR data, especially in parts of the UK where the only data available is in ascii format due to the information on the Environment Agency website.

The process I used involved using LASTools and also ArcGIS Pro although I'm pretty certain it can be completed without the last part (especially as I've only got 8 days left on my free trial!!!)

If you download the ascii raster images from the environment agency website (listed as a composite dsm or dtm file) you can then use the LASTools txt2las convertor to change the files to *.las files. These however don't work straight away with Chad's tool as the LIDAR data is unclassified. This is where ArcGIS pro is used to convert the las files to classified datasets and then processing those in Chad's tool have yielded a workable file that appears to be correct and match up with the OSM data... see below for my first attempt for Bishop Auckland golf club in the UK.

So in short, this is using raster ascii files rather than full on LIDAR las files but it does seem to give us a workaround should we need it.
I'm going to see if I can use the LASTools classify feature in order to avoid the need for ArcGIS Pro and then hopefully we will have a free way of doing it.

Andy

I tried downloading the files but they come out as *.asc and it doesn't appear to be a supported format on LAStools within ArcGIS - how did you work around that? many thanks

[andyf]

Hi Pat, I run the LASTools as a separate program and not from within ArcGIS. In the download folder of LASTools there is a bin folder that has the standalone programs in there.

Look for the txt2las.exe and run that

You then need to go to the browse tab on the left hand side and in the bit that is highlighted as E:\ change that to navigate to your folder with the asc files in it. Then in the box that has *.txt as the type manually change that to *.asc and then hit the Go button.

That should then download all of the asc files into the blank box at the top left of the screen.

Once they are in there, in the bottom right of the screen there should be an output box showing laz as the output file type. You need to change that to las and then click on either run32 or run64.

After a few minutes then check in your folder where you had the asc files and you should now see a whole load of .las files.

Once you have them stored in there then you can open up ArcGIS and start a new map project.

Then go into the map tab and click on add data. Navigate to your folder with the new las files and highlight all of them to import them

Once they are imported then a new menu at the top of the screen should appear titled 'Classification'. Go into that and there is a button to 'automatically classify' and you can pick classify ground.

This then opens up a new box on the right side of the screen and you need to then click on each file in the browse menu individually and click the run button on the bottom of the box to stat to classify the data.

Once you've finished the classification part then you can open up Chad's tool as per normal and just process the LIDAR data from there.

Hope that helps

Andy

[paddyjk19]

Really appreciate all your help Andy, that's exactly what I needed with my lack of PC literacy!

[paddyjk19]

Did you put anything for DEM Resolution whilst classifying? also did you just use standard classification or aggressive classification? thanks

[andyf]

I just used standard classification.

If you have a lot of points that are sharp edged cliffs next to pretty flat spots then it's best to classify it twice, once with standard classification and then do a 2nd aggressive one where the cliffs etc are but you can always modify the terrain in the designer if you don't go down that route.

Andy

[chadgolf]

The free lastools classification fuzzes the data enough to ruin putting greens. :/

[andyf]

Dec 2, 2019 19:19:58 GMT -5 chadgolf said:

The free lastools classification fuzzes the data enough to ruin putting greens. :/

That's not good. Might have to look into alternative options then although I'm guessing you've had a look yourself?

Andy

[jord088]

Nov 25, 2019 14:49:49 GMT -5 andyf said:

This is something I've just done for someone over on the HB forums however hopefully it'll help here for those who don't have full on proper LIDAR data, especially in parts of the UK where the only data available is in ascii format due to the information on the Environment Agency website.

The process I used involved using LASTools and also ArcGIS Pro although I'm pretty certain it can be completed without the last part (especially as I've only got 8 days left on my free trial!!!)

If you download the ascii raster images from the environment agency website (listed as a composite dsm or dtm file) you can then use the LASTools txt2las convertor to change the files to *.las files. These however don't work straight away with Chad's tool as the LIDAR data is unclassified. This is where ArcGIS pro is used to convert the las files to classified datasets and then processing those in Chad's tool have yielded a workable file that appears to be correct and match up with the OSM data... see below for my first attempt for Bishop Auckland golf club in the UK.

So in short, this is using raster ascii files rather than full on LIDAR las files but it does seem to give us a workaround should we need it.
I'm going to see if I can use the LASTools classify feature in order to avoid the need for ArcGIS Pro and then hopefully we will have a free way of doing it.

Andy

Does this still work? I have found LIDAR data for an area in Wales I’d like to use, I also downloaded to jpg images as i could only download 10km square at a time. I have found the 2 squares of data I need (dsm) which covers my golf course but as they are in asc format was wondering if I could still convert to las. Been searching everywhere today to find an answer!

Thanks

[jord088]

Nov 26, 2019 4:13:32 GMT -5 andyf said:

Hi Pat, I run the LASTools as a separate program and not from within ArcGIS. In the download folder of LASTools there is a bin folder that has the standalone programs in there.

Look for the txt2las.exe and run that

You then need to go to the browse tab on the left hand side and in the bit that is highlighted as E:\ change that to navigate to your folder with the asc files in it. Then in the box that has *.txt as the type manually change that to *.asc and then hit the Go button.

That should then download all of the asc files into the blank box at the top left of the screen.

Once they are in there, in the bottom right of the screen there should be an output box showing laz as the output file type. You need to change that to las and then click on either run32 or run64.

After a few minutes then check in your folder where you had the asc files and you should now see a whole load of .las files.

Once you have them stored in there then you can open up ArcGIS and start a new map project.

Then go into the map tab and click on add data. Navigate to your folder with the new las files and highlight all of them to import them

Once they are imported then a new menu at the top of the screen should appear titled 'Classification'. Go into that and there is a button to 'automatically classify' and you can pick classify ground.

This then opens up a new box on the right side of the screen and you need to then click on each file in the browse menu individually and click the run button on the bottom of the box to stat to classify the data.

Once you've finished the classification part then you can open up Chad's tool as per normal and just process the LIDAR data from there.

Hope that helps

Andy

Hi mate, not sure if you can help me. I managed to get this far but cant seem to get the data in the correct area. I tried setting spatial reference to OSBG as specified on website where I retrieved the data but still no luck. I classified first, thinking that could be the problem but I tried again without but still no luck. Thanks