During this lab you will work on building, displaying and manipulating digital elevation models (DEMs). You will build on what you learned in last week’s lab, but this time build your own DEMs from raw topographic survey data. The skills you develop are critical in terms of understanding how to convert raw vector data into interpolated surfaces from which additional spatial analyses can be done. Although we use elevation as the 3D data to build a surface from, these same skills apply to any type of spatial data you can interpolate (e.g. temperature, pressure, habitat quality, gravity, etc.).
The only prerequisite for this lab is a basic proficiency in using ArcGIS 10 (e.g. Lab 1 and Getting Oriented). It is also expected that you are familiar with the 6 C’s to make effective maps.
This lab is intended to make you proficient in the construction of DEMs from raw topographic survey data . The lab not only gives you experience working with DEMs, but many of the skills you develop here are more generally applicable to dealing with raster datasets in general. By the end of the lab, you will have:
Meets Course Learning Outcomes 2, 3 & 5.
As with all labs… This is a fictitious scenario!
You are still working for the environmental consulting firm (Big Cheese Watershed Management) which specializes in watershed management. Your boss asked you to build some DEMs from raw data provided by a client for a new project in Oregon and he wants you to put together your figures and findings on a couple of project pages (your lab pages). The pages will be used to illustrate for the client the variety of DEM data available for their project and to help them understand the differences between the data types.
His vague instructions and context can be summarized as follows:
“We got another project out in Central Oregon working for NOAA as part of their ISEMP program. We’ll be helping them make sense of some monitoring data from restoration work they are doing out there. They had an airborne LiDaR flight flown back in 2005 of the whole stream and they’ve been monitoring individual stream reaches within this area with rtkGPS topographic surveys since then. They have not built DEMs of their data yet and I want to take one of their reaches (Pats Cabin Reach) and show them what we can do with their data.”
“They’ve given us their raw GPS survey data, which includes both the individual topographic survey points and breaklines they surveyed in and some water’s edge data. Build a DEM of the reach and overlay a water depth map on it.”
“That LiDaR survey they had flown back in 2005 was by Watershed Sciences, and is now publicly available on the Open Topography portal. Go download the raw bare earth point data and construct a DEM for the same reach to provide a little more landscape context and demonstrate the resolution differences between the raw survey data and Lidar.”
“There has been a lot of geomorphic activity along this reach. Analyze the DEMs to quantify change in the channel and map the areas of erosion and deposition. Then build a tool to automate this change detection analysis process for the rest of us.”
Prepare a webpage(s) for this lab on your personal website for the course and prepare the following within that page or subpages:
For Task 1:
Set of informal figures illustrating
Provide a figure that makes a formal comparison illustrating the differences between DEMs derived from the same TIN at different resolutions **(e.g. 0.05 m, 0.10 m, 0.15 m, 0.20 m, 0.25 m, 1.0 m, ) (NOTE: choose a scale/extent that illustrates the differences at **all resolutions - focus on a feature)
Choose the most appropriate resolution at which to model this topography with a raster DEM. Justify your choice in a brief discussion about the resolution of the raw survey data and what you know about raster creation processes.
Provide a figure displaying your final DEM (of resolution chosen for analysis) w/ water depth layer (include resolution in figure caption)
For Task 2:
For Task 3:
Provide a figure that effectively displays the results of your change detection analysis
Provide a screenshot of your model with a caption that fully describes how the model works and what it does.
Make sure your lab conforms to the general lab submission guidelines. Submit a URL for this lab’s webpage.
Lab 7 Slides - Shannon Belmont Spring 2013
Subpages (3): Task 1 - Ground Based Topography Task 2 - Airborne LiDaR Task 3 - Change detection analysis