Mount St. Helens Pre-1980 Experience for Microsoft Flight Simulator X - Recreating Pre-1980 Terrain Elevation
As most of the pre-1980 Mount St. Helens terrain elevation does not exist in the form of a DEM, or Digital Elevation Model, I am having to recreate that DEM myself using geospatial data processing software. For the last few days I have been immersing myself into the workings of QGis - an open source geospatial data processing application very similar to the ArcGIS software professional mapping agencies and the USGS use, to create and author DEM and other forms of geospatial data. Yesterday, I began a series of tests on working with ESRI Shapefile data and creating test contour maps, then importing them in another open source geospatial data processing application known as SAGA. It is here, where I applied the elevation data in a TIN (triangulated interface network) format to create and compile a 3D model of those test contour maps.
As a test of those learned skills, earlier this afternoon I decided to trace contours in a small area going up from Spirit Lake's pre-eruption elevation contour of 3,198 feet. For reference, today's lake elevation is 3,406 feet! The small area I chose was the dividing ridge between the east and west lobes of Spirit Lake. Once I selected the area in question, I then proceeded to trace every contour on one gridded section of that ridge in a 1958 topographic map, using a vector layer, with each contour assigned an elevation point corresponding to the 80-foot contour interval of the source reference map. (It was a PAIN IN THE ARSE to do this, since I had to convert the numbers in feet, to meters every time!).
After tracing the final contour in QGis, I then exported it as an ESRI Shapefile, then imported it into SAGA, to which I then did a triangulating extrapolation of that contour data into a working digital elevation model. That elevation model's dataset was then loaded back into QGis as a DEM file, and subsequently exported as a GeoTIFF.
Once a brief test was initiated in FSX, I was ASTOUNDED at the height difference between present-day Spirit Lake and the former shoreline. It shows up best at the lakeshore (where I had placed an exclusion flatten of the lake to eliminate scenery artifiacting) on the dividing ridge, and where Harry Truman's resort is.
Now the fun part begins... Tracing a crap-ton of contour data, then extracting it into height map data, and then finally, off to the SIM.
Now for a few images showing the sequence of steps I followed, then a series of screenshots in FSX showing the change in topography.
Mount St. Helens Pre-1980 Experience for Microsoft Flight Simulator X - Recreating Pre-1980 Terrain Elevation
As most of the pre-1980 Mount St. Helens terrain elevation does not exist in the form of a DEM, or Digital Elevation Model, I am having to recreate that DEM myself using geospatial data processing software. For the last few days I have been immersing myself into the workings of QGis - an open source geospatial data processing application very similar to the ArcGIS software professional mapping agencies and the USGS use, to create and author DEM and other forms of geospatial data. Yesterday, I began a series of tests on working with ESRI Shapefile data and creating test contour maps, then importing them in another open source geospatial data processing application known as SAGA. It is here, where I applied the elevation data in a TIN (triangulated interface network) format to create and compile a 3D model of those test contour maps.
As a test of those learned skills, earlier this afternoon I decided to trace contours in a small area going up from Spirit Lake's pre-eruption elevation contour of 3,198 feet. For reference, today's lake elevation is 3,406 feet! The small area I chose was the dividing ridge between the east and west lobes of Spirit Lake. Once I selected the area in question, I then proceeded to trace every contour on one gridded section of that ridge in a 1958 topographic map, using a vector layer, with each contour assigned an elevation point corresponding to the 80-foot contour interval of the source reference map. (It was a PAIN IN THE ARSE to do this, since I had to convert the numbers in feet, to meters every time!).
After tracing the final contour in QGis, I then exported it as an ESRI Shapefile, then imported it into SAGA, to which I then did a triangulating extrapolation of that contour data into a working digital elevation model. That elevation model's dataset was then loaded back into QGis as a DEM file, and subsequently exported as a GeoTIFF.
Once a brief test was initiated in FSX, I was ASTOUNDED at the height difference between present-day Spirit Lake and the former shoreline. It shows up best at the lakeshore (where I had placed an exclusion flatten of the lake to eliminate scenery artifiacting) on the dividing ridge, and where Harry Truman's resort is.
Now the fun part begins... Tracing a crap-ton of contour data, then extracting it into height map data, and then finally, off to the SIM.
Now for a few images showing the sequence of steps I followed, then a series of screenshots in FSX showing the change in topography.