- Get DEM files from National Map download tool
- Set Area of Interest: Selectable Polygon -> Select... -> US State or Territory
- then click a state on map to select it
- Or Set Area of Interest: Map Extent/Geometry -> Click Extent -> Draw a rectangle on map
- After area selected, search for:
- Elevation Products (3DEP) -> 1/3 arc-second or 1 arc second
- Click search products
- Download TIF Files manually OR...
- Click TXT icon to download text file with list of data URLs
- remove all lines that are not tifs manually or with regex: ^((?!.tif$).)*$\n
- install and open uGet (https://sourceforge.net/projects/urlget/)
- File -> Batch -> Open TXT File
- Use "Mark By Filter..." to filter & only download TIF files
- Need shapefiles - vector representation of state outlines or outlines of map boundary etc.
- Get state shapefiles from: https://www.census.gov/geographies/mapping-files/time-series/geo/carto-boundary-file.html https://www2.census.gov/geo/tiger/GENZ2018/shp/cb_2018_us_state_500k.zip
- The file cb_2018_us_state_500k has all states - need to split into several files
- Create QGIS Project
- Add vector layer -> cb_2018_us_state_500k.shx (state outlines downloaded above)
- Vector -> Data Management Tools -> Split Vector Layer & set NAME as unique ID field
- Drag all the TIF files downloaded above into QGIS
- Raster -> Misc -> Merge
- Select all layers, set High Compression and save to file
- Decide on a projection - ESRI:102003 is good for US states (Albers Contiguous US)
- Reproject merged raster layer in QGIS: Raster -> Projections -> Warp (reproject)
- Enter desired target CRS
- If size is unmanageable, downscale at this step
- (ie. after reproject, ideally, because reproject loses resolution)
- Raster -> Raster calculator -> modify # of rows/columns
- DEMto3D supports exaggeration up to 10x
- If you want more than that, precalculate it here with raster calculator
- Raster -> Raster Calculator -> "layer@1" * 5 (for 5x exaggeration)
- Add state outline vector to project
- Vector -> Data management -> Reproject
- set target to same projection as raster
- Add state file from above as a new vector layer in same project as raster data
- Raster -> Extraction -> Clip by Mask layer
- Select mask (state vector) and raster (combined terrain) layers, set high compression, save to file
- Open clipped file from above in new QGIS project, or hide/remove other layers
- Confirm your CRS setting (USA_Contiguous_Albers_Equal_Area_Conic or desired projection)
- Set project background color to black
- Set terrain layer min to 0 (sea level) or whatever you want
- Project -> Import/Export -> Export map to image
- Can import raster data directly into PixelCNC and generate G-code
- However, as of now (v1.43) PixelCNC does not have a post-processor for Easel
- Coming soon in v1.44
- Could use standard GRBL post with different G-code sender (Candle, UGS)
- Install QGIS DEMto3D plugin using QGIS Plugin Manager
// didn't take detailed notes on using DEMto3D - but this is my preferred method
// read the DEMto3D docs and tweak settings to your liking
// consider terrain exaggeration - anything more than ~6-7x exaggeration looks implausibly spiky