This Weeks Lab
- BGet Some Data Together
- Using DEM and RGB data in Terrain Bender
- Burning vectors into raster layers
- Exporting your work
Get Some Data Together
Trim data from vectors – make DEM from point data
Find out where you want to do your study – Quesnel Lake today
We are going to find out what map sheets we need to create a data set from. In this lab we are going to use an area aroung Quesnel Lake. We are going to use 1:20 000 trim map sheets to make up a DEM. We are going to make use of the old TRIM storage form (SAIF), so we will have to convert it to something PCI can make use of. First we need to find out the map sheet we want.
- Open up QGIS and load the layer in /home/labs/geog457/quesnel_lake/trim_2000_mapgrid
- Use the OpenLayers plugin to load the satellite imagery from bing (web–> OpenLayers –> Bing Maps –> Bing Aerial)
- Load the path/row shape file in /home/labs/geog457/shape_file_data
Now we can determine what Landsat 8 Layer we would like to use for the lab and which 1:20 000 mapsheets we are going to grab. For the lab we are going to use a rectangle starting at 93A044 – 93A077. Determine what path and row we would need to grab.
The data is held in zip files one for each 1L20000 map sheet. Scott has unzipped all the files and put the saif files in:
/home/labs/geog457/quesnel_lake/trim_saif_files. We are only going to use one to test, but Scott has created a dataset that has all the mapsheets necessary for the lab.
Login to Osmotar and Open up FME Workbench.
This is a really brilliant piece of software, and Scott will walk you through setting up your workspace to translate the data necessary for building our own DEM layers. Once you have it set up, you should have a workspace looking like the image below:
Run the translation using the 93a065 mapsheet.
QGIS – create a study area
Create a study area shape file by selecting the mapsheets we will be building our 3D representation (rectangle 93A 044 – 077).
Save selection –> UTM zone 10 Nad 83 (26910)
Reload the new this new layer and dissolve the polygons to create one boundary polygon.
QGIS – create a lakes vector layer
Lakes as a vector Layer
Option 1 – Select from an vector dataset
Load the 93a_vri dataset from the vri_data directory in the quesnel_lake folder
Select only lakes from the layer using NP_DESC = “L”
Save selection as a shape file clipped to the study area in UTM 10 – 26910
Option 2 – PCI, what we should do in this class – but takes too long
Classify out the lakes and export them as a vector file
PCI -Subset out your landsat data
- Open up the boundary dissolved boundary layer created in QGIS
- Open the Landsat 8 scene Scott has downloaded (whichever one you want to use – September or July)
- Clip out the Landsat image to the extent of the vector layer
QGIS – View the data and DEM created in FME
- Load the vectors created in FME
- How do they look – what about the breaklines?
- Load the DEM – how does it look?
PCI – create a DEM and shaded relief from the vectors created from FME
- Create the DEM as we have done before
- You can set the pixel size to whatever you wish, but you may as well use the same resolution as the Landsat scene.
- How does this DEM look
- Create a shaded relief from the DEm
- subset the DEM and shaded relief using the extents of the subsetted Landsat scene.
PCI – export the DEM to a ESRI ASCII Grid
- Export the clipped DEM layer to an ascii grid (grd file – ESRI ASCII GRID)
Loading your DEM into Terrain Bender
Terrain Bender – Open Source Visualization Software
Look at the terrain bender site http://www.terraincartography.com/terrainbender, to see what it is all about. It is an Open Source software that runs via Java and can be used on all three operating systems (Windows, Linux and Mac). If you find it interesting to use, you can use it at home as well.
There should be a new icon on your desktop called Terrrain Bender. If there is not, Scott will help you find it. Start the program up and see if you can figure out how to load the DEM data. Once it is loaded manipulate the scene to get a perspective and “look and feel” that appeals to you.
Once you have data in Terrain Bender, you can really go to town with how data is represented. There are many parameters you can play with, such as:
- shifting the presentation – the bend
- the exaggeration
- the perspective
- the shading – sun angle and such
- hipsometric tints
You can load a texture image on top of the rendered DEM as well – you need to create the image first though
Make a map in PCI to drape over the DEM
Start a fresh project in PCI and load in your DEM, shaded relief, and the Landsat Image in a 654 stretched view. Then play with the look and feel of the project.
Play with the layers
- Set the transparency of the Landsat (top layer) to see the shaded relief below
- Set the transparency of the relief layer to see the DEM below it (DEM is the lowest level)
- Perhaps reload the DEM as a Pseudo Colour layer
- Load in the Lakes vector layer and colour it accordingly (perhaps a subtle pattern blue)
Cut out the white edges
- Switch to map view
- Set the page size (unnamed map) to match the data area (new area)
Export the map to bring into Terrain Bender
- File export
- Use a tif file format
- Resolution of 300
- Accept all other defaults
InkScape to dress it up a bit
You can add all sorts of stuff to the texture image through the use of InkScape
- Add a grid to the map
- Print the map with only the grid turned on (postscript file)
- Open up inkscape
- create a layer called image – then import the tiff you created by exporting
- create a grid layer – then import the grid layer
- lock the image layer
- select the grid –> object –> ungroup
- play around with moving all the labels and grid lines inside the image boundary
- maybe change the colour of the grid labels
- export as an image –> png file
Bring in the exported image(s) you have as a texture layer in Terrain Bender
You can add remove and add whatever texture layers you created in Terrain Bender to create your 3D perspective. In the end you should have something like this:
Saving an image for documentation
For the end of the class, we would like you to prepare two images to hand in for review. We would like two images that present something particular about the landscape in your study area. For instance you may have a textured image (with the RGB) that portrays the avalanche shoots well, or a hipsometric image presenting mountain steepness in relation to the lakes.
To do this set your level of detail to a reasonable resolution, and then use the export rendering function to save it as a png.