Week 4: Distance and Azimuth Survey

Introduction:
 One cannot always rely on technology to always be functioning perfectly. A backup device or plan is usually a good idea, for example when the first version of apple maps came out I'm sure those iPhone users wish they had a highway map instead. When out surveying landscapes the device you are using may not pick up a signal or just plain run out of battery, without use of that technology it could end up being more effective to go back to the bronze age of geographic surveying, a compass and ruler. For this week's activity we went out and surveyed a 1/4 hectacre plot of land using a TruPulse 360 azimuth, distance and elevation laser and we also used a compass and distance finder.

Methods:
 The study area my group chose to work with was based on the goal of surveying for 50 nodes. We chose a plot of land on 'upper campus' of University of Wisconsin - Eau Claire with a good amount of trees, Frisbee Golf holes, and other miscellaneous items found on a college campus.(Figure 4-1) Our geographical selection was a generally flat surface so we found our origin and got to surveying.
 The TruPulse 360 (Figure 4-2) is capable of emitting an invisible infrared energy pulse that determines the distance by measuring the time it takes for each pulse to travel to the target and back to the TruPulse. Once the measurement is complete, it is displayed on the viewing screen inside of the view hole. The readings can come back as slope distance, azimuth, inclination, horizontal distance and vertical distance. Our group made use of the horizontal distance and azimuth tools the TruPulse provided.  The other method we used was a compass and electronic distance finder. The distance finder was a two piece instrument that sent out a radio signal to the counterpart and returned and measured out the distance, much like the TruPulse, but with only one function and not nearly as fascinating.
 The compass we used was very accurate once adjusted for the declination. Magnetic declination is the angle between the compass north and the true north. Figure 4-3 shows and example of magnetic declination with a positive variation from geographic north. When the declination is affecting your measurements it is important to adjust the compass, there is usually a small screw to fix the issue. Luckily in Eau Claire, WI our declination is very minimal, 0 degrees and 59 min West, so we had only the slightest adjustment to make. The readings off the compass were made while holding the slit in the side of the compass up to one eye, while there you can see both your target and the reading of azimuth.
 Once we decided on the point of origin, just off the corner of Horan Hall, we began surveying points. I used the TruPulse while my partner recorded the measurements I was reading off. We had another group of colleagues alongside of us, they used the compass and distance finder and we later collaborated our efforts in completion of the activity. I used the TruPulse's capabilities to measure the azimuth and horizontal distance to each tree as we recorded across our 1/4 hectacre. Our group only found so many trees, and so we began recording readings to other features, garbage cans, emergency posts, signs, Frisbee Golf holes, and even a sign post.
 Once the surveying was done we entered the data into an Excel file. We had to make a field for the distance, azimuth, point data, and point number. (Figure4-4) Once the file was brought into ArcMap I set up a Geodatabase to house all the data. The table was exported and before I could run the Bearing Distance to Line tool I realized it was necessary to give each data point the point of origin for the surveying. Unfortunately we did not have a definite location for the survey location, as a result I went into ArcMap and opened the Bing Basemap and created a point feature class and created a point at the survey origin. Once the point was created I took the (x,y) data from the origin point and entered it into the Excel file for each point. When the new table was brought into the geodatabase the tool was completed. I ran the tool for each of the surveying that was done, the TruPulse and the compass with the distance finder.

Discussion:
 The accuracy of the results were difficult to compare, as our groups measured together we didn't stand in the same place of origin. This clearly threw our data off by a few degrees and meters here and there, we stood close together but the difference of a foot or two certainly had its toll on the results. (Figure 4-5) When I plotted the points there were issues with making the Bearing Distance to Line tool produce the results in the proper place. The original point of origin I made was done outside of a geodatabase with a non-defined spatial reference. The displacement of the result was close to the proper origin, but not close enough to call accurate to any measure. (Figure4-6)
 When viewing the results of the tool I took into question the accuracy of the entire methodology that we used. As you can see from Figure 4-4 the view that I had for the points on the bottom right corner of the image was not possible, how could I measure through the corner of the building. The other readings, red points, were done closer to the building and they had no issue getting measurements of the points in the bottom right corner of the image. Though none of the points are where they are supposed to be, (Figure 4-7) it is strange to see such a glaring inaccuracy with the TruPulse measurement methodology. The main issue is that the points are not where they are supposed to be, the blue points represent the actual location we were attempting to measure for, the Compass (red) are fairly close to where they are supposed to be considering the distance away from the origin they are. But the TruPulse points (green) are very far off from where they are supposed to be. However, from looking at these maps it is harder to detect the issue that arose, possibly it was measurement communication error, it could be error in the spatial reference. There are a handful of things it could have been.

Conclusion:
  Unfortunately our group was stifled with not enough nodes to measure, we got up to 32 but were unable to get accurate measurements of many others due to interference from previously measured nodes. Also another issue that I had was the inaccuracy of the data at the end of the activity, as I said before I would like to find the origin of this error. This activity was very useful in learning how to use surveying equipment and deducting the best way to record data that is taken. My only wish is that these few labs could be done when it is warm outside, I'm sure that would decrease all error that is arising.