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Lab 02 - Coordinate Data, Projections & Transformations

Introduction & Purpose of Exercise

This lab was meant to show the importance of coordinate systems and transformations. Using the real world data from Bear Creek Valley Study Site and the CHaMP Transformation tool the data is transformed from an unknown assumed coordinate system to UTM zone 12N.  For full details of the assignement or to try it your self see the instructors website

Methods

Task 1

To Begin this assignment I downloaded and unzipped the folder with the file geodatabase about the Bear Valley Creek Study Site in Idaho. I then added the four feature classes (Control_point, Topo_points, Hard_breaklines, and Soft_breaklines). After I had done this I adjusted symbology, and added labels using the labels feature in the Control points properties using the description field as the label. I then added a grid to show the unprojected nature of the map, to do this I right-clicked the data frame and added a grid by way of the grid tab, and put in 25 and 25 for parameters and added a light gray background to set it off from the page background.

Task 2

From the first part of the assignment where the data stayed unprojected the objective of this part was to use the CHaMP Transformation Tool to transform the data in to a spatial space. First I downloaded the CSV excel sheet with the coordinates of benchmarks in NAD 1983 UTM zone 12N, and used them to get in the right neck of the woods. I then used these coordinates to input into the CHaMP Transformation Tool. To use it I told it that it was in UTM zone 12N, and then copy and pasted the information from the CSV File into the dialog box, Northings, Eastings and Elevation. To set the output I just navigated to the area where the rest of the information was, I then choose benchmark one for the rotate to first option and then benchmark two for the second option. After it had been redrawn, and I then chose the from 3/ GPS 2 option because it had the least amount of error and fit the best on the map. 

Task 3

For this last task I had to take the transformed data and display it in both a PDF format and an interactive Google map. To do this I added a Bing areal base map and made it look pretty. I then used the Convert Map to KMZ File tool to create the interactive Google map.

Results

Task 1

Task 1 (Bear Creek Study Site Unprojected)

To download the PDF click here

The map shown here uses an assumed coordinate system. This is because there is no coordinate system assigned, it is laid out on a Cartesian coordinate system, which has that has no spatial reference. This limits the data are shown with the grid, with no spatial reference its just a nice point and line plot.












Task 2 & 3


To download the PDF click here

There are many different ways to transform data in ArcGIS, the one used to make this map was an affine transformation. Because it moved and did not scale the results. For this map the residual errors where from 3cm to 1 meter. It was the smallest combination of errors and looked the best on the shore line. I think the transformation was successful because it shows up in the right place and has the correct shape.












Bear Creek Valley Study Site Interactive Google Map

View Larger Map

Conclusions

Why is it necessary to transform data? Even though ArcGIS can reproject information on the fly, it can be safer to tell it what the coordinate system is. Letting decide how to show things could be inaccurate and manually inputting the coordinate system keeps things more correct. "Garbage in garbage out."
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Lab2_Task2.kmz
(34k)
Seneca Francis,
Jan 20, 2012, 6:26 PM
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