Distacne/Azimuth Survey Methods

Introduction

Figure 1.1 Tru Pulse Laser modern way of
 collecting distance and azimuth

This week in our lab we where tasked by Dr. Hupy to collect a total of one hundred points with accurate geospatial coordinates to be overlaid on a base map of the campus. Now although the task seemed easy, it acquired a very challenging twist when we where informed we where not able to use a GPS. To most of the class this now seemed like an impossible task. However, to our luck Dr. Hupy was kind enough to enlighten us on a technique know as distance Azimuth which allows a surveyor to collect points in a field where they would be unable to stand by or get an accurate reading with a GPS to collect them from a neutral point determine the angle difference and distance and place the point based off of that additional information. This lab will not only inform all of us of a new technique but it will allow us to travel into the past and experience how historically points where collected.



Figure 1.2 Suunto compass used to collect azimuth

Originally the class had two forms of collecting the data we could either use a Tru Pulse Laser (figure 1.1) which was a hand held advanced range finder that calculated the azimuth and distance in one device or we could use the older version being the handheld Suunto compass (figure 1.2) and the Sonin Distance Measurement (figure 1.3). The later tools where standalone tools where one would find the Azimuth , Suunto compass, and one would find the distance away from the point of origin, Sonin distance measurement. Both methods where one in the same but our group had originally practiced with the two tool method and decided to continue with that for our collection. We also felt that with the complications of the laser being in a different magnetic declination we where worried the points would not come out right. The area that we had chosen to collect from was in the center of our lower campus quad. We thought by collecting from the center of the quad and collecting all of the block seats and any of the standing trees and light post we would be able to stand in one location and collect all hundred points. Although we soon ran into complications with the distance measurement we were able to collect all hundred points.




Figure 1.3 Sonin Distance measurement

Methods

Initially the class needed to obtain a background on how the tools operated. In this situation we went out as a class Monday and familiarized ourselves with both the tools for measurement but also how we needed to input our collection onto an excel spread sheet and how to import the data into ArcMap. Once out for the practice trial all of the groups were able to familiarize themselves with one of the two collection methods. As for the case of Katie and myself we took the two tool approach using the Sonin and the Suunto compass. Once we had collected a couple of points and found that we needed to input our data into six columns to allow for proper operations within ArcMap (figure 1.4)
 we now where ready for our true collection. From here Katie and I where able to set up in our original collection area. To start we needed to establish a coordinate of origin. We used Katie's phone to collect this point but fond later on in our display that her phone was not very accurate and skewed most of our data points to not fall on our wanted targets. However, for the purpose of the activity we continued with the collection. We then needed to have one member from our group walk with the receiving end of the distance caliper to stand next to the object. During this the other member was able to locate using the compass was able to collect the Azimuth angle based on 360 degree circle from our origin. With both the distance and angle collected at each point the process was very similar throughout collection. The only variation was toward the end when we needed to relocate to two different origin points for we where unable to collect distance readings once we reached a 50 meter distance.

Figure 1.4  Completed table of our six columns needed for proper input into Arcmap

Once we had collected the data in the field we then needed to display that data in ArcMap. To accomplish this there was a few steps that needed to be taken. First we needed to create our own geodatabase located in our personalized q drive folder for Geospatial field methods. Then we could import the data table making sure that all fields where input correctly. Meaning the x field was the latitude coordinate of our origin, the Y field was the longitude coordinate, the distance was our distance column, and the angle was our azimuth. With all of these fields input correctly we could use the bearing distant to line tool to input our azimuth collection. The bearing distance to line tool takes the point of origin and the angle and distance to calculate how far and in what direction each point is from the original collection origin. The results are as follows in figure 2.1


Figure 2.1:  completed display with bearing distance tool run and overlaid on
the county of eau Claire base map quadrant 29 NW







Although once we are at this pint we where not completed we then needed to run one last tool to transfer these new lines with end nodes into point features. To accomplish this we needed to run a second tool being feature vertices to pint data management tool. This tool allows to take the completed layer from bearing distance to line feature and turn all of the lines with end nodes into standalone point features. Giving us our final points needed to be displayed (figure 2.2).

 

Figure 2.2 Final display of our 100 points collected in our Distance/Azimuth survey for geospatial field methods

 

 

Discussion

As our final tool was run we where very shocked with the output. We found that the first two rows of seats where mainly accurate and held decent geospatial accuracy. However, we quickly found that the farther away from the origin point we where the more inaccurate our azimuth became and the distance became skewed from the correct value. After looking into past blogs we found this to be a similar case with groups that used both the laser and the compass. All of the groups from each semester had found similar complications being that the farther the object was from the point of origin the more complicated accurate azimuth and distance readings where. The complication was either due to poor techniques in collection in greater magnetic disorder form the laser or compass. We also found that depending on the base map picture one used the data points matched up better than others. This was due to different projected coordinate systems or due to timing of the picture for some photos where not from the new construction and didn't included the trees recently planted.

 

Conclusion

In total the lab was very eye opening to not only see and experience a new way of collecting it also allowed us to have another tool in our belt for any point in our carrier that we might need anomalous  means of collection. Also with the story from Dr. Hupy about having his GPS and collection gear being confiscated during travel it give us an idea to always have a backup plan for collection whenever heading into the field.

 

However, WE have also learned from this lab that like in any other task in life there is always a proper tool for each situation, some cases call for accurate measurements and can be collected form GPS units, others can not be collected using GPS and have to be collected form distance and azimuth collection but require more detail to collection for it is harder to have accurate readings unless more time and effort is put into have direct line of sight and flat ground to each object. Along with knowing when you need to move to a new spot to have closer more precise readings on your data points to take away from the collector error possible in longer more complicated collections. All together the lab was very successful for it showed us a new way of collecting but also challenged us to use more primitive means of collecting and not rely on our technology that we seem to take for granted and assume it will always be there for us. For like in this case and many others we might not always have our perfect tools to carry the weight and when life hands you lemons sometimes you just need to make lemonade.