Field Activity #4: Azimuth Survey

Introduction

Today new equipment is being developed at a high rate which is making old techniques near to obsolete, however when working in the field technology has a tendency to fail its user. Techniques get passed down from geographer to geographer and is invaluable when the fancy gadgets fail. While new technology makes the collection of spatial data much easier and time efficient it can also be plagued with flaws because it only understands what you give it and not the entire circumstance like the human mind does. The total cost for these new data collection equipment can be through the roof as well. Some equipment though can be considered as reliable and cost effective such as a compass or tape measure.

All things considered, it is necessary that geographers retain the knowledge and skills that can be derived by more basic tools and techniques. In the field activity that it described below the utilization of several tools was necessary to collect data to create a basic survey of objects in Eau Claire, WI. The tools used included a laser distance finder, tape measure, and TruPulse device. The tool that was used the most was the TruPulse because it could derive distance and azimuth which were paramount for this project. The device had several other functions and one that had been used by groups in the past included the height function which tells you the height of an object using trigonometry.

The goal of this lab was to survey several objects in the field by gathering their species/attributes, azimuth degrees and distance from base points. The next goal included getting GPS points for the data which would allow each group to put their data into ArcGIS where they could be mapped and analyzed for accuracy. The major goal of this lab was to  use several techniques of surveying in order to gain a broader understanding of the differing ways to do it.

Study Area

The study area of our group was located on upper campus and specifically located around Governors Hall. The points chosen from where the survey was taken place were all located at location where many objects of varying attributes could be located. The group utilized three different points to survey the region. Some different types of attributes that were surveyed included trees (oak and pine), snowmen, snow piles, cars, signs, etc. Image 1 below shows the Area of Interest of the group with the yellow dots representing the points that were surveyed.

Image 1: The image above shows a zoomed portion of the University of Wisconsin - Eau Claire's campus. The dots reflect our points that we survey which will be covered further in the sections below.

The study area as seen in the above image isn't currently cleared so the surface is much more obscured due to the snow cover. However the snow did help to create new features on the landscape including snow forts, snow mounds and snowmen. In image 2 below it is apparent just how deep the snow actually is. This deep snow made the survey much more difficult to traverse.

Image 2: This image shows myself, Cody Kroening, in the snow on the day of the survey. The snow was often up to my knee and sometimes above in the drifted zones. The temperatures were also below zero, which was the first time it had been that low during the day in about a week.

Magnetic Declination Web Service

Magnetic declination, or the angle between magnetic north and true north, is a tool that can be utilized when calculating variables such azimuth. Another important note to make is that declination values east of true north are positive while west values are negative. Magnetic declination isn't a solidified value and actually will change over time. Click here to learn more about declination and calculating it in your city.

Image 3: The image above shows the site where longitude and latitude values can be typed in to calculated the declination in your city. There are several other variables that can be typed in to calculate declination.

Image 4: The image shows a PDF copy of what is created from image 3 above. The declination is calculated and given given to the person desiring the data. The declination is used for calculating azimuth data which is important to this field activity.

TruPulse 360 Rangefinder

The TruPulse line of rangefinders come in several different levels, however our department owns the specific model 360. The 360 contains a compass within its core which allows for azimuth readings, which was perfect for the survey project. The 360 also gives distance values, height values, inclination and much more. This device was used in the survey through its distance value and state of the art azimuth data. These values, when combined with GPS values, can be mapped in software packages such as ArcGIS. The device is simply pointed at an object where it then uses its laser system to take measurements. These measurements are then presented to the user on the screen. To learn more about TruPulse devices here.

Image  5: The image above shows the Geography department's TruPulse 360 model. This device is described thoroughly above. Not only does this device work out in the dry western states but also works in below zero temperatures in desolate Wisconsin.

Methods

Several methods were utilized using several different techniques to retrieve the final results for the group. All of these methods were compiled and normalized in order to map them. After the points were mapped they were compared with a base map to check for accuracy.

Image 6: The above image shows some of the snowmen that were recorded during the surveying process along with one of the large piles of snow that found its way into our entries as well.

The initial step in the surveying process began with picking a location and time to survey. Our group chose to survey on Friday, February 21st after the big snow storm, which turned out to be a bad idea since the snow was incredibly deep. The amount snow that Eau Claire received over the weekend actually allowed students to create large snowmen that can be observed in image 6 above. We then chose to do our survey around Governors Hall, which also happens to be the hall that I am a Resident Assistant in. Our first location was against the back fence behind the building. The second location was on the other side of the building near the "smokers picnic table." The final surveying point was at the front door of Governors Hall. Some of the surveyed points contained snow forts and trees much like in image 7 below. The technique that we used with the TruPulse included one of us using the device to tell the azimuth and distance to the recorder. The recorder would then put the distance, azimuth, and feature type into the field notebook which can be seen in image 8 below. The process of surveying over 100 points took just over an hour in total.

Image 7: The above images show both one of the pine trees and snow forts that we surveyed in our field activity. This fort was assembled the night of the snow storm from last night. 

Image 8: This image shows the method of data collection by the recorder. We included columns for distance, azimuth and the type of feature that we were recording.

The next phase of the project was to find the location of each point in decimal degrees through the use of bing maps. After the locations latitude and longitude were found then were then recorded into the excel file as x and y coordinates. The data can be see presented below in image 9. As can be seen in the image, the feature along with its number, azimuth, distance and attribute were all recorded in order to get an accurate survey of the desired location. Before the table could be put into arc for analysis a geodatabase had to be created. This was done by using ArcCatalog. In the catalog I followed the folder connection file to my folder where I then right clicked and selected new. From new I was able to create a new file geodatabase. This database was used for the entire exercise and contained all of the data that I would need to compute my results.

Image 9: This image shows the normalized table results with the latitude and longitude data. The table was then transferred into ArcGIS where it could be created into point data for easy transposition onto a base map.

The next step in the analysis of the data included bringing the table from excel into ArcMap where it could be made into point data by utilizing the "Bearing Distance to Line Command" located in ArcToolbox. This tool uses your data to create a brand new feature class that includes a bearing field, x and y coordinates, and a distance field. The output feature class has several lines which extend from a focal point. The focal point is the place where the data was recorded while the end of each line represents a feature that was used in the survey. The final step in the creation of the images was to use the "Feature Vertices to Points Command" which takes vertices of input features and makes output points in the dataset.

Image 10: The above image shows the output feature class that is produced via the "Bearing Distance to Line Command." The ends of the orange lines, which will have points attached to them in the images below, represent features in the survey.

Results

As can be seen in image 11 below if your GPS points are even slightly off then the whole image could be potentially compromised. Our data turned out fairly well and we seemed to only be a few meters off from the actual objects. When looking at image 11 it is apparent that some of the azimuths could have been slightly skewed since some objects are being placed on the buildings. We did utilize three of the doors to the building as features, but we also had a few stray signs converging upon the Governors Hall walls.

Image 11: This image shows the results of the "Feature Vertices to Point Command." Each yellow points represents a feature in the survey. Many of the points were near to perfect or only a meter off, but a few converged with the building, which was not actually where they were located.

Discussion

I think that your survey went very well despite the weather conditions that we had to face. I do think that the weather may have caused some of the azimuth values to vary because of how cold it was. I was in charge of taking most of the points using the TruPulse device and I would be lying if I said that I wasn't shaking slightly from the cold. Along with that, it was tough to stay in exactly the same spot when spinning around taking all of the points. On several occasions I found myself slipping further into the snow and even falling when trying to spin like a top to get more points. The snow was well above my knees at several locations which made it hard to stand still since my pants were freezing to my legs. It is essential to try to not move from your point so you can get accurate azimuth data so standing in the snow is something that I would avoid if I were to try this field activity again.

Another portion of the lab that made it difficult was trying to get the best possible position for each of the points without losing any integrity from the data. As can be seen in images 1, 10 and 11 above the points were slightly skewed and I would mainly blame this on inaccurate GPS locations.

Overall I would highly recommend this surveying method because if you don't have a surveying station near by, but you do have the right equipment then this strategy can be efficient and accurate down to a meter or so.

Conclusion

When all is said and done, I would have to say that I really enjoyed this lab even though I had to trudge through knee high snow to get it done. I was able to learn about azimuth and how to accurately survey using many different tools. All of the tools that were presented to us are powerful in their own right as surveying instruments and could potentially be my tools of the trade once I graduate. I hope to learn more about working in the field over the rest of the semester since each lab so far has given me valuable skills in the real world and job market.