Lab 02 – Coordinate Data, Projections & Transformations – Advanced GIS Courses: WATS USU

Please download the file, which contains the CBW05583_028709_2011-08-15.gdb file geodatabase for the Bear Valley Creek Study Site. Bring the raw survey data into an empty ArcMap document, and create a map with a measured grid overlay to display the data, denote the different types of data, label the benchmarks, and illustrate that the data is unprojected in an assumed Cartesian coordinate system. While not spatially referenced, this data DOES have scale. It was collected in meters against the assumed grid. You will notice that there are a number of data layers and some of them are empty. Please ONLY use the following layers for this task: When finished, include a static version of this map in your website. Save your map (maybe as Task 1) and quit ArcMap. The key to transforming any data from one coordinate system to another coordinate system is having some coordinate values for the same points (typically 2-5) in BOTH coordinate systems. In our case, we want to transform survey data in un-projected assumed Cartesian coordinate space to real world projected coordinates (NAD 83 UTM Zone 12 N), and we have three benchmarks to do it. The benchmarks were surveyed in with both a total station (very precise: +/- 5 mm) in an assumed coordinate system, and in real world coordinates with a very inaccurate hand held GPS (+/- 5 m). However, using the GPS coordinates as a basis for a simple affine transformation (i.e. a shift, rotate and datum adjustment), these coordinates will be good enough for GIS overlay purposes. The cartoon below illustrates conceptually the process of shifting and rotating the total station survey data using the GPS coordinates of the same points. In the example below, BM3 is used as the point around which the transformation is based (click on image for larger view). You will use the CHaMP Transformation Tool to help you. Source.

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Last Modified: April 22, 2016 @ 11:02 pm