Exercise 11 - Navigation with Map & Compass

Introduction

This week we went out to a local property owned by the university called The Priory which we used as our navigation site for using a map and compass. The navigation maps we created in exercise 3 (fig. 1) will be used to navigate to 5 points around The Priory. We were to just use a compass to find each point and navigate from point to point.

Map of The Priory from exercise 3 used during the navigation session. (fig. 1)

Methods

The only things we could use for travelling from point to point were the map of The Priory and an orienteering compass (fig. 2). This exercise will strengthen our navigation skills and hopefully prevent us from ever getting lost; we're geographers after all.

An orienteering compass used during the orientation session to lead us point to point. (fig. 2)

We first mapped out each of the five points and the start point and drew a line from the start line to each point in order of how we were to navigate. Our group had to start with point 5 and move to points 1, 2, 3, 4 and then back to the start point. We first needed to measure the distance from point to point and convert that into footsteps. We simply measured the distance in centimeters, converted that into meters on the ground and then converted that into footsteps by using the stride-length per 100 meters that we measured back in exercise 3. Once we had the lines drawn to each point we determined the azimuth we were to follow from point to point. To do this we lined up the arrow on the compass with the line from the start point to the next point (with the arrow facing the direction we wanted to go) and then lined north arrow with north on the map. Once we had north facing the right way the arrow would show what the azimuth is from the point that we started from to the point we were going to.

Once we had written down all of the azimuths we needed to from each point to point we could start the journey. The first point was at 320 degrees, so we set the arrow to point at 320 degrees and put the north arrow inside of the red outline because 320 degrees only means something if you know where north (0 degrees) is. This is also called 'putting the red in the shed' as in putting the red north arrow in the red outline or shed.

Once we knew the direction we were to go, one person would stand at the starting location while the next person would walk in the direction of the azimuth while staying in sight of the person standing at the start location. To make the explanation easier lets call the person standing at the start point with the compass, the navigator and the person walking ahead toward the next point, the scout. When the scout was far enough away the navigator would confirm that they were at the correct azimuth from the start point and they would then leave the start point and walk to the scout. The navigator would then take the exact position of the scout and the scout would then walk to another point in the correct direction from the navigator. This would be repeated until the scout had gone far enough to be at the correct destination based on the number of footsteps we had determined at the beginning. We would then move the compass to the next azimuth to navigate to the next point. At every point we would repeat this process until we had navigated to every point and had ended up back at the start point.

Discussion

This whole process took about two hours and it was a perfect day with no clouds and it was a nice 70 degrees. We had some trouble because we had mapped the start point incorrectly and had to redraw the lines to each point which changed the distance and azimuth for each path from point to point. After that we had little trouble finding each point however, some difficulties did occur when we came across dips and crevasses because they made it more difficult to stay on course and navigate through the thick forest.

When we were navigating from point to point we would almost always be off from directly hitting the point, but we were never off by more than 10 meters. This is some surprising accuracy giving that we just had a map and a compass.

Conclusion

I was very surprised how close we were to actually directly hitting the points given that we had just drawn the lines from point to point and walked in the right direction. If we had even been off by a few degrees we could have completely missed the target points. The use of map and compass is very important in terms of navigation and geography skills and is a valuable skill to have. 

Exercise 9 & 10 - Topographic Survey (Dual Frequency GPS & Total Station)

Introduction

For this exercise we were creating a elevation map of the campus mall using two different techniques to capture the points we needed. We were to use both a Dual Frequency GPS and a more accurate Total Station technique. For exercise 9 we used the Dual Frequency GPS and the following we in exercise 10 we used the Total Station. After we have collected points with both of these techniques we will be able to compare and contrast the benefits of each technique. Below is the study area (fig. 1) of the campus mall here at UWEC. The photo is about two years old and shows the campus mall during initial construction in 2013.

Study Area of the campus mall at UW-Eau Claire (shown during construction in 2013) (fig. 1)

Methods

The first technique is the Dual Frequency GPS which uses both a TopCon HiPer (fig. 2) and a TopCon Tesla (fig. 3). These devices work together to give us very accurate GPS data points which are produced by the HiPer and recorded wirelessly with the Tesla using the Magnet application. The HiPer sits on top of a rod supported by two legs and the Tesla is attached directly to the rod using a clamp. To collect a point you just make sure the rod is perpendicular to the ground using the built-in level and save the point in the Magnet application on the Tesla. The Tesla takes multiple points and averages them out to provide a more reliable reading. This method is very easy to do and quick, however the accuracy is not as good as a total station.

A TopCon HiPer SR unit used in the Dual Frequency method (fig. 2)

A TopCon Tesla unit used in the Dual Frequency method (fig. 3)

The other technique is a Total Station GPS which uses a TopCon Total Station (fig. 4) as well as a TopCon Tesla from the previous technique. This technique is different that the Dual Frequency method in that it stays stationary while another person moves a prism target (fig. 5) on top of a rod around to collect points. First we need to collect a occupy point and a back-site point using the TopCon HiPer and Tesla. The occupy point is determined by the height of the total station and the exact coordinates of where it sits. The back-site is collected using the HiPer at a point away from the occupy point in order to set azimuth. This will allow us to collect points with the Total Station by calculating the direction and elevation of the total station unit from the collected points. Next, the other person goes to each point we are to collect and holds the prism target while the total station operator collects a point by shooting a laser at the target which gives us the distance and direction. It collects the point by knowing how high the target is above the ground and the laser gives the distance and direction from the occupy point that the total station is standing on.

A TopCon Total Station unit (fig. 4)

A prism target used with the TopCon Total Station as the point collection indicator (fig. 5)

Once we had collected all of the data we were able to export the data from the TopCon Tesla to ArcGIS. The data came in a text file (fig. 6) as seen below which can be imported into ArcGIS by importing the x and y data. It is also important to make sure to set the projection before converting the text file into a point feature class, otherwise the data is distorted and doesn't show up in the correct locations.

Text file exported from the TopCon Tesla giving the corrdinates of the points collected for each technique. (fig. 6)

Once the data is in ArcGIS, we can put the satellite image behind the data and the maps below are created. The first (fig. 7) was created using the Dual Frequency method while the second (fig. 8) was created using the Total Station method.

Data points collected by the Dual Frequency GPS unit. (fig. 7)

The Dual Frequency method shows very accurate points and many more data points due to the ease at which it was to collect these points. It was very easy to collect points with the method and we were able to collect many points very quickly.

Data points collected by the Total Station unit. (fig. 8)

The Total Station method shows also very accurate points although due to the long setup time it takes to get the TopCon ready to collect points and we ran out of time. We still had enough points to create a descent interpolation seen below.

Once we had the points I created Spline interpolation rasters for both techniques. The first (fig. 9) is of the points gathered using the Dual Frequency method while the second (fig. 10) is from the points gathered using the Total Station method.

Spline interpolation of the points gathered using the Dual Frequency technique. (fig. 9)

This interpolation shows very detailed terrain due to the large number of points we collected. There are however, large variations in the elevation that are not represented correctly such as the same hill and dip in the left side of the map which is not there in reality. 

A Spline interpolation from the the points gathered using the Total Station technique. (fig. 10)

The interpolation from the Total Station is accurate in terms of what the actual landscape is like, but it lacks in terms of detail due to the low number of points collected by us.

Discussion

In the Dual Frequency method there was a hill and dip in the left side of the map that should not be there and this could be due inaccuracy in the elevation data collected by the Dual Frequency method. This lead me to believe that the Dual Frequency method isn't the most accurate method even though it is very easy and quick. This could also just be explained by user error, which is possible.

During the setup of the Total Station we had trouble figuring out how to get the back-site point set and then it took a little while practicing shooting the laser before we were able to start collecting points. If we had finished the setup more quickly we would of been able to collect more points and have a more detailed terrain model for the Total Station method.

In terms of which technique is better, I would definitely say that the the Total Station is the superior technique. Even though it takes a while to setup, it is very easy to collect points once it is ready to go. Also, now that I have had experience in setting it up, it would go much more quickly the second time.

Conclusion

If I were to re-do the data collection for this exercise I would have collected more points in the Total Station because it would have given me the most accurate and detailed terrain model of the study area. I believe the Total Station to be the best of the two techniques. If I needed to map out a terrain for a future project or for my future job I would definitely go with the Total Station technique because it gives you a more accurate model. Once it is setup it can collect a large amount of points very quickly which would provide a more detailed model.

Exercise 8 - Distance & Azimuth

Introduction

In this exercise we learned how to map out objects within a area using only distance and azimuth to find there locations. This method of mapping can be used as a substitute for when the collection of GPS coordinates is not possible. We split the class into groups of two and each picked an area to map out. We needed a 1/4 by 1 hectare area as our study area. This exercise will help us troubleshoot problems when we are faced with situations when we don't have access to the proper GPS equipment and need to map an area out using different methods.

Distance and azimuth is a method of mapping that using a benchmark location where the data collector stands and collects information of objects nearby without actually mapping those objects. To do this we use a laser distance finder which when pointed at an object can give use the distance away from us that object is (in meters) as well as the azimuth or direction that object is from us (in degrees). We then use ArcGIS to map out these objects given their distance and azimuth from the benchmark location.

A TruPulse Laser Distance Finder that we used to find the distance and azimuth. (fig 1)

Methods

The study area that we chose to map was a local park near campus called Randall Park. It is a small park the size of a city block with trees, benches, sidewalks, a statue and a swing-set. We chose this area because it meet the 1/4 by 1 hectare plot requirement and had a lot of open space for us to map out the area easily. This area was also used in previous classes which is where we got the idea.

We were going to first chose starting locations for use as a benchmark. We chose do have four benchmarks in each corner of the study area and we used the left corners of the sidewalk as these benchmarks. We first needed to collect the coordinates of these points and write them down. We chose to use a laptop with excel instead of a pen and paper in order to streamline the post processing needed later. We had a table with four attributes: point number, distance, azimuth and attribute information. Each point will also include the coordinates of the benchmark that corresponds to that object. We were to collect 100 points.

Out in the field we started by collecting the coordinates of the first benchmark location using a Trimble GPS unit. Once we had our starting location we set up our TruPulse laser unit up on a tripod directly above the benchmark and starting collecting information on each object. We picked trees, benches, lamp posts and other things and collected their distance and azimuth from our benchmark. The TruPulse worked by clicking the collect button when the cross-hairs in the eyepiece focused on the object we wanted and it would collect the distance in meters and azimuth in degrees and display the information above. We repeated this process for all 100 points and moved to three more benchmarks with a total of four benchmarks. Once we had finished we had a table with all of the points with their distance and azimuth from their respective benchmarks and their attribute information (what kind of object there were).

Next we needed to input the information into ArcGIS. To do this we first needed to set up a geodatabase for the project because the tool we ran needed to have a table that is in a geodatabase. We then put our excel spreadsheet table into this geodatabase. The first tool we ran Bearing Distance to Line tool (fig. 2) which could be found under Data Management and Features in ArcToolbox.

The Bearing Distance to Line tool which gives us the line features based on the benchmark locations and the distance/azimuth from those points. (fig. 2)

The image above shows the tool with the table as the input, the x field as our longitude of our benchmarks, the y field as our latitude of our benchmarks, distance field as our distance column and bearing field as our azimuth column. Below (fig. 3) shows the line features that were created from the table.

The output from the Bearing Distance to Line tool showing the line features created from the table. (fig. 3)

Next we needed to then create point features from the lines that we created in the previous step. To do this we use the Feature Vertices to Points tool (fig. 4) which can be found under Data Management and then Features in the ArcToolbox. 

Feature Vertices to Points tool used to create points from the line feature class from the previous step. (fig. 4)

We just input the line feature class from the previous step and the output (fig. 5) should give us points at the ends of all the lines. Below you can see the output and the point feature class that was created which is all of the objects that we collected data on in the field.

The line feature class including the point feature class created from it, showing where all of the objects we collected data from in the field. (fig. 5) 

Discussion

The data collection in the field went off without any major problems and we really didn't have any trouble with the equipment. There were some problems that we faced in the post processing however. The first problem was with the table and running the tools because we couldn't get the Bearing Distance to Line tool to work until I realized that it was not in a geodatabase which is required for these tools.

Next when we go the line feature class to show finally the benchmark points were off by a meter or two due the inaccuracy of the GPS unit we had been using to collect the coordinates for the benchmark locations. To fix this I used the satellite image that we used as a base map and found the coordinates of the corners of the sidewalk using the identify tool and moved the benchmarks to those locations. This solved the problems with the benchmark being off, but the accuracy of this method was still not great.

The final map (fig. 5) shows points that are off of the study area that we used and this can either be inaccuracy of our data collection (most likely) or shortcomings of the data collecting technique. These points are minimal however and the majority of the points seem pretty accurate after I moved the benchmarks to their proper locations.

Conclusion

This technique has many benefits such as when you are without a proper GPS that could map out these objects but you have a benchmark of something that you can find on a satellite image later or you already know what the coordinates are. This technique has been surpassed by technology like the total system GPS units and other GPS units that can map out object very accurately without having to take down distance and azimuth. This technique also isn't as accurate as other more recent methods however, when the time comes that you don't have access to the proper technology this is a very viable alternative.