rossoe 46 Posted January 16, 2019 Having posted a previous tutorial regarding working with Terra Incognita and QGIS to manage satellite imagery ready for use in Terrain Builder - I have since discovered that due to an update to GDAL (2.4.0) one of the key steps in that tutorial using 'Clip Raster by Mask Layer' no longer works perfectly! So I reworked the tutorial by getting a bit more under the hood and using GDAL command line where possible, this also simplifies the process a little and reduced even further processing on the data. This process has often been described using Global Mapper, but I wanted to detail the equivalent steps within the open source (free) GIS app - QGIS. The goal was to achieve an export satellite image and heightmap with the same or better quality than would be possible with Global Mapper. The following software versions were used for this tutorial: QGIS v3.4.3 Terra Incognita v245 I have referenced Terra Incognita because I felt it was the easiest way to obtain satellite data in the oziexplorer map format - see this tutorial for help using Terra Incognita. Don't worry about getting the perfect square sat image using Terra Incognita, just grab slightly bigger area than you will actually use for this project - QGIS steps below will cut to the perfect square. First an overview of the steps required: For Heightmap: Load heightmap into QGIS (drag and drop) Set QGIS to appropriate CRS for location of your HM Create shapefile & generate perfect square using Advanced Digitizing panel Obtain extents from square feature Run 2 GDAL commands First to set cell size, CRS and then clip to shapefile square extents Second to convert to .asc file For Satellite image For single tile export Load in just the '.map' files generated from Terra Incognita into QGIS Merge rasters Obtain extents from square feature gdalwarp command will set cell size, CRS and then clip to shapefile square extents For 4 tile export (large projects 40960 size and above) Load in just the '.map' files generated from Terra Incognita into QGIS Merge Rasters Create grid – 2 x 2 Feature (using square generated above - heightmap step) Move each quarter to its own shapefile layer Obtain extents from each quarter feature Run gdalwarp command for each quarter to set cell size and CRS and clip to shapefile square extents And now detailed steps for: Heightmap This tutorial covers single raster heightmap as per the kind you will find on opentopo here, I will detail steps for heightmaps spread across muliptle rasters in another update. as they will require additional steps likely including Merge / Build Virtual Raster commands. This section does not cover any re scaling of heightmap, which I would recommend against anyway. Remember Grid size x Cell size should = the same size (meters) as your source heightmap selection. Drag and drop your heightmap '.asc' into QGIS If you do use opentopo for source of Heightmap, make sure extract both the .asc and .prj files before proceeding with below. They should both be in the zip file from opentopo. Set QGIS to appropriate CRS for location of your HM Clicking on the CRS section bottom right within QGIS – will bring up the Project Properties for CRS Select the CRS to match your real world data, in this example its ‘WGS 84 UTM zone 20N’ because the terrain is from the Montserrat in the Caribbean. See also UTM projection. This will ensure your QGIS project space works appropriately with any other data you want to add - eg road shapefiles etc. Terrain Builder will only use UTM 31N but we'll get to that later. Create shapefile & generate square feature using Advanced Digitizing panel Top menu – Layer > Create Layer > New Shapefile Layer Save to project folder location Change Geometry type to ‘Polygon’ Match CRS so it is the same as that just configured in above step Right click on your shapefile in layers window & select ‘Toggle Editing’ From menu – View → Toolbars → Advanced Digitizing Toolbar Select ‘Add Polygon Feature’ Select Enable advanced digitizing tools To create a perfect square, left mouse click for your top left starting point, move your mouse to the right a little, then press ‘d’ on keyboard, type in the exact width (distance) required (in this example ‘20480’) then immediately press Enter – be careful not to move the mouse before pressing Enter or it will mess up the number. Press left mouse click and you will have drawn your first horizontal line which turns red. By default this tool snaps to 90 degree angles, making it easy to draw your lines. Now to draw the vertical line start moving mouse your down, press ‘d’ again and type in same figure as above, press Enter and another left mouse click, repeat the process for the last 2 lines of the square. See a short video example using the Advanced Digitizing tool: After the last left mouse click from the step above, the tool is still waiting to plot more points, so to finalise the square do a right mouse click This will then bring up an attributes dialogue – just type any number and Enter Save the above edits to the shapefile by clicking on the layer & selecting ‘Toggle Editing’ Obtain extents from square feature Activate the toolbox if it is not already available Start typing 'vector' in Processing Toolbox search bar, and you will see 'Vector information' Double click it and make sure your square input layer is selected - then just click Run You will only need to copy the Extent figures, which we will use within the GDAL commands in the next step Run the first GDAL command which will - set CRS, cell size and then clip to shapefile square extents From menu - Plugins > Python Console Click 'Show Editor' The blank window on the right is where you will paste GDAL commands Now you are ready to edit the command below to match your data - sections in bold are the parts to edit: import os os.system(r'''gdalwarp -t_srs EPSG:32620 -wo SOURCE_EXTRA=1000 -tr 5.0 5.0 -srcnodata "-9999" -r cubic -ot Float32 -of GTiff -te 576787.687480 1841104.815839 597267.687480 1861584.815839 D:/Arma/Heightmaps/Opentopo/output_srtm.asc D:/Arma/QGIS/Montserrat/converted.tif''') Some explanation of the key parameters within above command: -t_srs EPSG:32620 CRS to match where the heightmap is from in the world. -tr 5.0 5.0 The desired resolution of your heightmap, match with Cell size set within your Mapframe properties in Terrain Builder: -te 576787.687480 1841104.815839 597267.687480 1861584.815839 The 4 long figures represent the extents of your square, and should be replaced with your own figures obtained in previous step. Input path: D:/Arma/Heightmaps/Opentopo/output_srtm.asc Output path: D:/Arma/QGIS/Montserrat/converted.tif Update the paths to match where you've stored your source heightmap, and where you want the output tif saved to. You will have to wrap your paths with quotation marks "..path.." if it contains any blanks (spaces), or just remove blanks entirely to avoid the confusion. Run second GDAL command - converting tif from above step to a Terrain Builder friendly .asc Remember to change the paths in below command to match where your files are located import os os.system(r'''gdal_translate -of AAIGrid D:/Arma/QGIS/Montserrat/converted.tif D:/Arma/QGIS/Montserrat/final.asc''') Satellite image For single tile export Load in just the .map files into QGIS Merge Rasters Top Menu - Raster → Miscellaneous → Merge Select all your .map files as input layers change Output data type to ‘Byte’ as the default is ‘Float32’. Select ‘Save to File’ under Merged – as the default is to a temporary file. Obtain extents from square feature You should already have this from working on heightmap above 576787.687480 1841104.815839 597267.687480 1861584.815839 Run GDAL command import os os.system(r'''gdalwarp -t_srs EPSG:32620 -wo SOURCE_EXTRA=1000 -tr 1.0 1.0 -r cubic -of BMP -te 576787.687480 1841104.815839 597267.687480 1861584.815839 D:/Arma/QGIS/Montserrat/merged.tif D:/Arma/QGIS/Montserrat/mont.bmp''') Some explanation of the key parameters: -t_srs EPSG:32620 Sets the CRS -tr 1.0 1.0 Sets the resolution of your satellite image to 1mtr per pixel - which is recommended. Make sure it matches your settings within Terrain Builder. -te 576787.687480 1841104.815839 597267.687480 1861584.815839 Clips to shapefile square extents For 4 tile export Detailing additional steps required for a 4 tile export – which would suit those terrains that are 40960px x 40960px and higher. Load in just the .map files into QGIS Merge rasters - same as above (single tile export) Create grid – 2 x 2 Feature You will need to have created the square shapefile first – see above steps Top Menu – View → Panels → Processing Toolbox Processing Toolbox Menu – Vector Creation > Create Grid Set Grid type to ‘Rectangle (polygon)’ & the Horizontal & Vertical to half the distance of your main square Set it to save new grid feature to .shp file After clicking 'Use Layer Extent' Select the shapefile layer for your square After clicking Run, your original square will then be Covered with a new grid of 4 tiles – perfect quarters of your original square Move each quarter to its own shapefile layer Because you will need to export each quarter separately for use in Terrain Builder, we will move each quarter onto its own shapefile layer. Click Select Features - And select the first quarter: Top Menu – Edit > Copy Features Then… Edit → Paste Features As → New Vector Layer Save shapefile layer to something obvious I’ve used ‘TL’ for top left. Repeat for the remaining quarters and you’ll have something like below, ‘Grid’ can be deleted. You will then have 4 tiles which we can use to gather each quarters extents Obtain extents from each quarter feature Copy extents to clipboard And list them out for safe keeping TL - Extent: (576787.687480, 1851344.815839) - (587027.687480, 1861584.815839) TR - Extent: (587027.687480, 1851344.815839) - (597267.687480, 1861584.815839) BL - Extent: (576787.687480, 1841104.815839) - (587027.687480, 1851344.815839) BR - Extent: (587027.687480, 1841104.815839) - (597267.687480, 1851344.815839) Run GDAL command for each quarter to set cell size and CRS and clip to shapefile square extents import os os.system(r'''gdalwarp -t_srs EPSG:32620 -wo SOURCE_EXTRA=1000 -tr 1.0 1.0 -r cubic -of BMP -te 576787.687480 1841104.815839 597267.687480 1861584.815839 D:/Arma/QGIS/Montserrat/merged.tif D:/Arma/QGIS/Montserrat/TR.bmp''') Loading your assets into Terrain Builder I would recommend saving copies of any files to be used in Terrain Builder into a separate terrain project folder. This will prevent your source project files being adversely affected, and potentially no longer working within QGIS - particularly relevant to those changes mentioned below. Heightmap (.asc) edits Open your asc in notepad and change the following to ensure it loads in Terrain builder: ncols 4096 nrows 4096 xllcorner 576787.687479999964 yllcorner 1841104.815839000046 cellsize 5.000000000000 NODATA_value -9999 ncols 4096 nrows 4096 xllcorner 200000 yllcorner 0 cellsize 5.000000000000 NODATA_value -9999.0 Save to a new asc, whilst maintaining the original for use in your QGIS project space Before loading the asc file into Terrain Builder, delete the .prj file. Otherwise it will not import into TB. Satellite image Before loading the satellite image into Terrrain Builder delete the .bmp.aux file Managing the project assets within QGIS Save your QGIS project so that you can return to export further data at a later date. Layers can be tidied up to hold the essentials ready for the next time you want to re-run GDAL commands, or export anything else like road shapefiles or mask layers etc. Road shapefile creation Load into QGIS (drag and drop) road shapefile In this example I got a good dataset from - https://data.humdata.org/ Clip vector to square shape Top Menu - Vector > Geoprocessing Tools > Clip Save features from clip to new shapefile - selecting correct CRS UTM-20 Top Menu - Layer > Save As Set road shapefile to CRS - 31N RMB on road shapefile > Set CRS > Set Layer CRS Set QGIS project CRS to UTM- 31N (bottom right corner): Collect extents from your square shapefile: Extent: (576787.687480, 1841104.815839) - (597267.687480, 1861584.815839) The first two values will be used in the v.transform step below. v.transform on road shapefile using calculated extents from square shapefile Your heightmap asc must adhere to Terrain Builders required values of easting 200000 and northing 0 Your road shapefile also needs to line up to the same values - we will use v.transform to achieve this So taking the extent values we grabbed in previous step - We will do the following calculations to bring these values to (200000 and 0): Easting: 576787.687480 - 376787.68748 = 200000 Northing: 1841104.815839 - 1841104.815839 = 0 -376787.68748 -1841104.815839 Having figured out the correct figures plug them into the v.transform process Drag and Drop into QGIS your heightmap asc - the one you are able to load into Terrain builder - already adjusted to (200000, 0) Set CRS on above asc to UTM - 31N Right click on asc in Layers > Zoom to Layer In Layers panel drag the asc below your transformed road shapefile - so you can see the roads layered above the asc Your roads should now be perfectly aligned above your heightmap Setting ID and ORDER fields RMB on transformed shapefile layer > Toggle Editing RMB on transformed shapefile layer > Open Attribute Table Click Delete field - select all fields and press OK New Field - Name 'ID' - length 0 New Field - Name 'ORDER' - length 0 Toggle - Multi Edit mode ID - Enter 0 - click Update All Select ORDER from drop down - Enter 1 - click Update all Click - Switch to table view and check that ID column all show as '0' and ORDER all show as '1' Click Save RMB on transformed road shapefile - Toggle Editing to save the changes Switching to Terrain Builder - Load your road shapefile Top menu - File > Import > Shapes Click OK Perfectly overlaid within Terrain builder: 3D Preview using Qgis2threejs If you want to see an instant 3d preview of your terrain within QGIS you can with the amazing plugin Qgis2threejs First install it: Top menu > Plugins > Manage and Install Plugins RMB on the Merged layer and select Zoom to Layer Then select both the Merged raster, and the original source heightmap - deselect all other layers Start the Qgis2threejs plugin - Top Menu > Web > Qgis2threejs > Qgis2threejs Exporter Select source heightmap and nothing else RMB on heightmap > Properties Set the Resampling level to 6 Set Resolution to 400% Enjoy browsing around your terrain in 3D: You can also export your terrain to a browser interface if you want - File > Export to web Coming Soon: - Assisted image classification - for creation of mask Above tutorial is also available on Github - https://github.com/rossoe/Arma3_QGIS 2 3 Share this post Link to post Share on other sites
GEORGE FLOROS GR 4206 Posted January 19, 2019 Thank you very much for the tutorial rossoe ! To be honest i started once creating a new Greek island : Samothraki https://en.wikipedia.org/wiki/Samothrace and unfortunately i stopped in the middle !!! Thanks again ! ( PS : I want some day to check this from scratch ! ) Share this post Link to post Share on other sites
rossoe 46 Posted January 27, 2019 Updated with road shapefile section - who needs Global Mapper! 1 Share this post Link to post Share on other sites
xXIMMIGRANTXx 0 Posted January 28, 2019 14 hours ago, rossoe said: Updated with road shapefile section - who needs Global Mapper! Hi Rossoe, I've gone through your tut on PMC site and just came upon this gem. This one seems to be updated with added details. I would definitely love to have GM, but too expensive for me. Are you able to provide it? Share this post Link to post Share on other sites
RoF 240 Posted January 28, 2019 5 hours ago, xXIMMIGRANTXx said: Hi Rossoe, I've gone through your tut on PMC site and just came upon this gem. This one seems to be updated with added details. I would definitely love to have GM, but too expensive for me. Are you able to provide it? You don't need GM, you can do all the same stuff in QGIS which is what this guide is for Share this post Link to post Share on other sites
rossoe 46 Posted February 12, 2019 Updated with guide on 3D Preview within QGIS using Qgis2threejs plugin 1 2 Share this post Link to post Share on other sites
GamersRoost 0 Posted June 30, 2019 You have no idea how much this helped me. I have been trying for literally 2 years to get terrain from a map file. I cannot express my thanks to you for going over such immense detail. GamersRoost Share this post Link to post Share on other sites
