Field Activity #4: Conducting a Distance Azimuth Survey.

Introduction

The fourth assignment in Geography of Field Methods was to conduct a distance azimuth survey using different geographic techniques.  The assignment called for students to find an open area where conducting many survey points could be easy to do.  These survey points were to be taken by a compass and a laser device to gather the distance and azimuth also, every point should have have some type of information attached with them.  After the points were gathered the next step is to enter them into an excel file and import them into ArcMap.  Then the bearing distance to line tool was used to plot the data on ArcMap to view the results of the points taken.   This activity was designed to have the class become familiar with taking distance and azimuth points using the laser device and a compass.  

Study Area

A big part of the assignment before any points could be taken, was picking a study area to conduct the survey.  The point on which to take points must be relatively open with no trees, poles, or any items that would block the image when looking at it from above.  The area must also have a good amount of features  to gather points, for example: trees, poles, garbage cans, or any item that is can be easily seen from a distance away.  Our group, Drew, Andrew, and I, choose our base point on the campus of University of Wisconsin Eau-Clair, in between Phillips and Schneider Hall and mapped points towards and away from campus.  However, after not running out of features to collect we decided to move into the campus mall to find more features to collect.  A total of 100 points were taken with three different base points.  

Figure 1: This image is showing 2 out 3 base points we used when collecting data.  The
3rd point can be seen in images below.  This aerial image of UWEC is very easy to use
because there are few trees.

Methods

Points were collected using two different instruments: a compass which determines azimuth and a laser device which determines distance, in meters, and azimuth.  Both techniques will be used when collecting points.  Just mentioned earlier the first step when conducting a distance azimuth survey is to find an area easy visible from an aerial photo but with many features to conduct the survey.  After finding the base point the next step is to complete the survey.  Our team of 3 decided to survey different types of features, trees, poles, garbage cans, bike racks, and tables.  Andrew used the laser device to collect points and Drew and I switched off collecting points with the compass and writing down the distance and azimuth of each point.  It is important to have two ways of collecting data in case one fails you, usually the technology.  As our course instructor, Dr. Joe Hupy says, "Technology will always fail you", for this reason it was important to collect the azimuth of the point with both the laser device and compass. 

Figure 2: This is an image of drew collecting data with the lazer device from our first base point.
By simply pressing a button the azimuth and distance are given on the screen of the device. 

Figure 3: It is very importing to remain in the same spot when collecting points.  Utilizing the snow we
made foot imprints to know where to stand each when surveying points. 

As each point was collected they were put into our notebook into four categories: number, azimuth, distance, and type.  The collection was done fairly quickly once the group got into a rhythm and really started to gather points.  We did have some troubles remembering which tree or pole we collected but it was corrected when tracing our steps backwards.  After collecting 50 points in between Phillips and Schneider hall we decided to go on to campus mall to collect 25 points at two locations.  This was done because the assignment called for 100 points to be collected.  The assignment also had us collect points with both the lazer and the compass.  For each point the lazer and compass were used and the two were compared, which can be seen later in this blog. 

Figure 4: The notebook which we used to combine our data.  It was sorted into to 4
different groups: Number, Distance, Azimuth and Type. 

After collecting the data the next step is to enter the data into an excel sheet and import it into ArcMap.  The four categories containing 100 points was entered into an excel sheet and six decimals were attached to the numbers.  It is important to attach six decimal points other wise for some reason ArcMap will not be able to use the data and the results will not be able to be seen.  Along with entering the data into excel the latitude and longitude of the three base points must be found.  Drew, group member, did this by using an app on his phone that collects an lat long point by just clicking a button.  Our first base point had an X, Y (latitude, longitude) of 44.79769, -91.499 as you can see in figure 5 below.

Figure 5: This is a portion of the excel sheet before it was entered into ArcMap.  6 decimal points were
used when importing it into to ArcMap. 

Magnetic declination is the angle between the magnetic north and the true north.  The compass will point to the magnetic north leaving room for error when collecting points.  NOAA has application  an that will calculate the degree of declination for any location.  Eau Claire the degree of declination is 1.36 degrees west (negative).  1.36 degrees was subtracted from ever azimuth collected form the laser and compass.

The next step of the assignment was to import the excel file into ArcMap and display it as a map.  First a geodatabase was created to store all the files that were going to be created and then a basemap was imported from USGS to show an image of UWEC's campus in 2013.  Next tools were used to create point and lines of the 100 different points collected.  The bearing distance to line tool was used, which can be found in Data Management>Features>Bearing distance to line, to give use a line from the base point to the point surveyed.  This tool was used three different times because we used three different base points.  The bearding distance to line tool would error when trying to only use one excel sheet instead of three because of the three different X, Y coordinates.   Also the two was ran twice for each point, once to get points from the lazer and points from the compass.  After the bearing distance to line box was filled out correctly the tool was completed and lines appeared on our map.  

Figure 6: this image is an example of the first two base points after using the bearing distance to line tool.
The yellow and gray lines are compass points and the red and purple lines are the lazer points. 

Next to add points onto the lines the lines the feature vertices to points tool was used.  This can be found in Data Management tools>Features>Feature Vertices To Points.  This tool will simply add a point on to the end of each line to make the map easier to understand and compare to the real world features.

Figure 7: this picture is showing the map after the tool, feature vertices
to points was used for the first two base points.

Once all of these process were down only little tweaks were needed to complete the final map.  The 100 lines with points all appeared on the map coming from three different base points.   The feature layers created were saved to the geodatabase and a projection of WGS 84 was used since latitude and longitude were being used instead of meters. 

Results

The final results of our map were fairly accurate.  I was not pleased with the difference between the compass and lazer collection, the compass was way to far off compared to the lazer and real world points.  This could be because we were not precise enough using the compass, the compass was damaged and not working correctly, or something else.  We did notice that the compass was not working correctly when we were standing next to the pole at our first base point as you can see in figure 2.  However, when we changed base points we were not next the the pole and the compass was still significantly off from the lazer azimuth points. 

Figure 8: This is a small to medium scale of the image.  All the points appear in lime green.  Some
error occurred as you can see points appearing in the street or on top of buildings which were not
surveyed by us.  However the our base points were very accurate because the app used by my partner drew.  

Figure 9: Red dots= Compass points.  Green dots= Laser point.  When comparing the two different
colors there is inconsistency.  In some cases they are very close to each-other in others they differ greatly.
Also sometimes the lazer point is way off and other times the compass point is off.  This makes it very
difficult to understand which device failed us.  

Conclusion

Overall the surveying tended to be somewhat accurate, combing both the compass and lazer points would give a very accurate map of the features surveyed in this area.  Our distance measurements were very accurate along with the base points being perfect.  This allowed us to only make errors when recording the azimuth.  The results we got were fairly good but could have been better and there is room for improvement if this assignment was done again.  With out us knowing if the lazer actually detecting the feature we wanted or bouncing off something else it can be less accurate than the compass, which I would have not predicted.  However, the compass failed at some points too, one reason could be magnetic disturbances but that should have affected the lazer too unless it takes this into account.  

Collecting data points can be done in many different ways, using azimuth and distance can give a quick an accurate results.  This can be done in almost any weather and can be done the old fashion way, the compass, or by using new technology, the lazer.  This activity has taught me that using new technology may not always be the best.  When looking at the results the lazer data points some are not accurate compared to the compass showing that in some cases it is wise to use both new and old technology.