Latest Contributions by JosselineLou

‎11-17-2013

Hi Joss, Well, I tried both, and neither looks too hopeful. One landed offshore in the Channel (north of Le Havre) and the other in the middle of northern France. Here's how I did it. I added the points as an event layer using Add XY Data in ArcMap. When setting the coordinate system, I choose WGS 1984 UTM Zone 31N, but then modified it to have a false northing of -5000000. Then I added the data again, but switched columns for the x and y values, again using the modified false northing. Can you narrow down the location beyond the coast of northwest France? Depending on how I look at it, I think it could be anywhere between Brest and Le Havre. Melita Thank you for the help, I hope you didn't spend too much time on that, the spot is located at the end the Authie river. I finally managed to find the right coordinates system, indeed, it was NTF Lambert North France. It's kind of weird that they didn't gave us the coordinate system in the first place. Thanks for the tips, it surely will get useful in future, Take care, Joss

‎11-13-2013

Have you checked with the data provider? Unfortunately, I'm studying right now and the teacher who gave me the data is unable to give any precisions. In fact, the data come from those who collect the them but we don't know who and how to reach them. Three files has been given, two ASCII files (mnt and mne) and one shema.ini file that contain : [authie_mne.asc] Format=CSVDelimited [authie_mnt.asc] Format=CSVDelimited Nothing more has been given to us so we've got a hard time to figure the coordinates system. Robert, How did you manage to use UTM? Northing values in northern France should be around 5.5million. So if I swap the order of the coordinates so that they're in northing easting z order, and add 5 million to the northings, than UTM 31 North looks like it might work. Other French systems just don't seem to fit, even if I swap the xy values. Melita Personnaly, the point cloud appears offshore of Nigeria when I use WGS84 UTM 31N coordinate system. How can I swap order of the coordinates or add 5 millions to the northings ? The point cloud looks like it is on the right longitude but on the wrong side of the equator... Thanks for your answers, Take care, Joss

‎11-12-2013

Hello, I have a problem here, indeed, I used an ASCII file from LIDAR data but I want now to define a coordinate system. When I open the ASCII file, it gave me a list of numbers : 545023.50 299909.50 8.33 545024.50 299909.50 8.70 545025.50 299909.50 8.80 545026.50 299909.50 8.79 545027.50 299909.50 9.01 545028.50 299909.50 8.41 545029.50 299909.50 8.52 545030.50 299909.50 8.54 545031.50 299909.50 9.11 ... I understand that it is X, Y and Z coordinates but I don't know in which coordinate system. Does anyone have an idea ? (It is supposed to be in the North of France, on the coast) Thanks in advance, Take care, Joss

‎10-15-2013

Thank you for your answer, I didn't know this Tool, it seems very interresting. Finally I just run the Basin Tool in the Hydrology section of the Spatial Analyst Toolbox and it gave me the differents basin I was looking for, the problem is that I mustn't create myself outlet points because I need to be able to run a modlel for every data possible. Thank you anyway for the Tool, Take care, Joss

‎10-14-2013

Hello, Sorry to monopolize the Hydro forum but I'm kind of stuck here, here's my problem : I've created a raster of streams from a flow accumulation raster using Raster Calculator : "flowacc" == Con("flowacc" > 100,1) The output raster is fine, it gave me the path of the streams as expected, but I can't order the Streams using Order Stream Tool. Indeed, I tried with both Strahler and Shreve but the raster doesn't shows up at all (it's created but is invisible). Maybe I've done something wrong in the previous steps, but I think I've followed the right process. Thanks in advance, Take care, Joss

‎10-14-2013

Hello, I need to create a model in ArcGIS in order to delineate streams and watershed. After resolving the problem of exporting streams, I encounter an other issue. Indeed, I need to automatically create several outlet batch points in order to create different polygon representing the differents watershed of the area I'm studying (The area will change depending on the data we will give me, that's why I need to get an automatization). So, I know there is in ArcHYDRO a tool to create outlet btach points but I need a tool to batch them automatically. Thanks in advance, Best regards, Joss

‎10-14-2013

Thanks, the Raster Calculator worked like a charm ! And as an additional tip when it comes to extracting stream lines from dem's... I always create a curvature surface and use that as a weighting into the flow accumulation step. Because of the math of the curvature function, upwardly concave areas (like a stream) are negative, so invert the curvature output first, (X -1) so that +ve values are associated with upwardly concave areas and -ve values indicate the top of the hill (for example). This idea comes from a paper by Tarboten & Ames from about 1992. Otherwise follow the steps in the hydrology section of the help files as suggested by Jim. Cheers, Neil Thank you for your answer first, but as I'm french, I didn't really understood, do you mean using the Curvature tool in 3D Analyst ? What are +ve and -ve values ? Thanks Regards, Joss

‎10-10-2013

Hello, I have a problem, I've created a flow accumulation raster from a flow direction raster (created from an elevation raster). But now I need to create a polyline feature of the channels but the Stream to Feature tools doesn't crash as I tried to process it. I'm kind of stuck here, thanks in advance, Joss

‎10-08-2013

I was wondering if it was possible to use a Python command that convert my .asc LIDAR data to .dbf in order to join to an attribute table. I also need to add field names. (This is a XYZ ASCII file) Thanks in advance, Take Care, Joss

‎10-07-2013

Thank you very much for the tip, it worked like a charm ! Take care, Joss

‎10-03-2013

Hello, I have a problem with clipping a raster, first of all, I had LIDAR files in .asc format, I created a point cloud shapefile out of it and try to interpolate the shape to have an elevation raster. That's where my problem is : - I first used Natural Neighbor tool, the raster was fine but as the point cloud is concave, ArcGIS filled the concavities where it should have let them empty. - I then created a polygon following the shape of the point cloud in order to run a clipping process, but after the clip done, the output raster was really pixelated. (I also tried the Extract by Mask tool, same problem) - Finally I tried an interpolation by Spline using Spline with Barriers tool choosing my polygon feature as extent but after one hour and eleven minutes of processing (indeed, 3 000 000 points cannot be interpolated in a minute) it crashed... Here I come trying to avoid nervous breakdown or burning down my computer, hoping that you're gonna come out with a brilliant idea. I'm just looking for a decent interpolation of a concave point cloud. Thanks in advance, Take care, Joss Edit : Here are two pictures of : first, the raster before clipping, interpolated using Natural Neighbor, second, the raster clipped using the polygon created from the point cloud. [ATTACH=CONFIG]27994[/ATTACH] [ATTACH=CONFIG]27995[/ATTACH]

‎10-02-2013

It might be late for an answer but it could help so I'm sharing my thoughts. There is a alternate way to create a polygon following the concave shape of a cloud point. First, I used the Point to Raster tool using those parameters : VALUE FIELD : whatever CELL ASSIGNMENT TYPE : COUNT PRIORITY FIELD : NONE It will create a raster following the shape of the point cloud, Then use the Raster to Polygon tool with the newly created raster input. (use value as field), it will create a polygon following the shape of your point cloud. Hope this works for you, Joss

‎10-01-2013

Thank you very much for your quick answer, it helped me very much. I finally used the ASCII 3D To Feature Class, I had a problem for getting the attribute table showing the elevation values in order to create an interpolated raster afterwards. But I resolved it by myself, thanks again for the post, I know now more about the data I'm dealing with ! I think I'm will use ERDAS to geolocalize the raster I will create (I have some aerial photography) Thank you again (for the third time I think). Take care, Josseline

‎09-28-2013

Hello, I recently acquired LIDAR files which are in .asc format. My objective is to create an automatic model using modelbuilder so any LIDAR files of a watershed area can be processed in order to extract paramters such as geographical extend... But I'm stuck at the first step, I have the raw LIDAR data in .asc format and when I open it in notepad++, it shows only 3 columns and about 3 millions rows of datas, the matter is that I have no spatial reference, I don't have any information such as : NCOLS xxx NROWS xxx XLLCORNER xxx YLLCORNER xxx CELLSIZE xxx NODATA_VALUE xxx I can specify myself the number of rows, columns and the nodata value but I can't specify the cellsize or the geographical extend of the dataset. I can't create a Raster using the ASCII to Raster Tool (which is strange by the way considering a raster doesn't need spatial references to exist). I'd like to know how I could convert such files into Raster data (preferably TIFF) which I can then specify spatial references. Thanks in advance, Josseline

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My Ideas

Latest Contributions by JosselineLou

Re: Unknown coordinates from ASCII file

Re: Unknown coordinates from ASCII file

Unknown coordinates from ASCII file

Re: Automatic implementation of Batch Point for Watersheds delineation

Stream ordering using Stream Order Tool

Automatic implementation of Batch Point for Watersheds delineation

Re: Create a network of polyline from a flow accumulation raster

Create a network of polyline from a flow accumulation raster

Converting ASCII (.asc) to DBASE (.dbf)

Re: Interpolating a concave point cloud avoiding pixelated raster output

Interpolating a concave point cloud avoiding pixelated raster output

Re: Points to Polygon "Footprint"

Re: LIDAR asc files without spatial references processing ArcGIS 10.0

LIDAR asc files without spatial references processing ArcGIS 10.0