GPS Navigation Exercise

Introduction

This week's exercise was closely related to the previous week's in that, once again, we were conducting a navigation exercise at the Priory. However, this week we employed a different, more modern technique of navigation. Instead of using a compass and map, all we had with us was a Garmin etrex GPS unit. This type of navigation has several advantages over the map and compass method. First of all, a GPS is way more compact and easy to utilize in the field than is fumbling around with a large map and compass. Secondly, it is way quicker to figure one's location on a GPS as well as finding one's way from point to point because the units are digitally displayed and are calculated in real time. With a map and compass, we had to slowly go through the methodology of figuring out azimuth and then pacing out the distance. This took a long time and got quite frustrating. Thirdly, a user can create a waypoint in the GPS of a particular point and then tell the GPS to find the fastest route to the point. This is a huge advantage over map and compass where the navigator can easily get off path. The only disadadvantage of a GPS is that it could fail in the field if the batteries are bad and then you better hope you packed a map and compass.
The Garmin etrex GPS unit is considered an older unit and can be purchased for relatively cheap. That said, it is still very capable for navigation purposes.

Fig. 1 - GPS unit used in navigation exercise.

Once familiar with the unit settings, the appropriate units should be set before navigating as well as double checking that the appropriate datum is set as well. In this case, the units were set to UTM, which are displayed in meters, which gives the navigator a higher accuracy then does decimal degree units. The datum was left alone at WGS84. In order to see how well we navigated, a track log was set up to display our actual track to each point throughout the course. The track log properties were set to "point", so that every defined time interval, a point was recorded with time and location. This is very useful for post-exercise analysis to be able to map out not only our track, but also to see the times it took to get from point to point. Each member of the group was issued their own GPS unit. It should also be mentioned that in the woods, the density of the forest can affect the positional dilution of precision (PDOP) on a GPS unit. Basically, the PDOP is the accuracy of a 3D position based on the number of satellites and their geometry. A low PDOP indicates a very accurate position. We didn't worry about this variable in this exercise, since we weren't doing any sort of measurements but it can be an important thing to be aware of when using a GPS.

Methodology

Once again, we were to retain our groups we were assigned from last week, but we would be navigating a different course. Each group had to navigate to 6 points, which locations were given to us again. This week Drew Peterson, Kory Dercks, and myself were 15 minutes late getting out to the field because the snow had trapped a certain individuals car in his driveway, hence we had to find another car to get to the field. By the time we got out to the field, the rest of the class had already started navigating. We were told to go to our respective starting points and then catch up to our groups. Drew and I caught up to my group and even though Drew wasn't originally in our group, he decided to stay with us since his group was doing the same course but backwards.

Fig. 2 - Drew Peterson, our adopted group member of the week.

Once all four of us were together, we took some time to debrief each other on how to navigate via GPS. Since we were using a UTM coordinate system, we knew that the coordinate display was showing a northing and an easting. As mentioned before in a previous post on coordinate systems, a UTM zone places the central meridian in the center of the zone and then anything east of the meridian is an easting and anything west of the meridian is a false easting to ensure positive values. Anything north of the meridian is a northing and anything south is a false northing to ensure positive values. For our purposes, all we knew we had to do was watch how the northing and easting values were changing to navigate from point to point. Since we had a sheet with all the points in UTM format, we could determine which way we had to go based on our current location. It's just a matter of knowing that the numbers will increase when moving north or east, or decrease when moving west or south and then figure out the difference from current location and the point location. We found out that it was easiest to match the northing and easting one at a time. What this means is that we would get our easting distance to match and then get the northing to match instead of trying to match both numbers at a time. This was sort of difficult to master at first but then after finding the first point, it became pretty easy.

Fig. 3 - Kent punching his card at the first point location.

 During the navigation exercise, I was playing around with the different functions of the GPS and found out that there was a way easier way to do the navigation. The user can create a waypoint with the point location coordinates and then hit the find button on the GPS interface. This prompts the unit to draw a track on the screen to the point from the current location and tells the user which direction to travel and also how many meters away it is. I don't feel like this is cheating since it is a component of the GPS and is a very effective and efficient way to navigate. We were also very comfortable following easting and northings at by that point anyways.

The navigation conditions were once again rather formiddable. It had snowed pretty heavily the night before which meant that the snow would be deeper this time. We found that in certain spots of the course, snow was knee high. This had a negative impact on the time it took us to navigate. Not only were we traversing through deep snow, but also over very hilly terrain. Most of the course was in the woods but we managed to find a nice road to walk on for different portions between point 4a and 6a. This route also took us along the holding pond of the Priory. This part of the walk smelled awful.

Fig. 4 - Me pointing to the holding pond area.

Fig. 5 - Beatriz taking a break in the snow.

Fig. 6 - Kent finding another flag.

Fig. 7 - Me checking the next point location.

After the field exercise was over with, we took our GPS units to the computer lab where we uploaded our point data into ArcMap. Once the points were in, they were overlaid on top of a high resolution aerial image of the navigation area as well with the points where the flags were located. From here, we were instructed to make 3 maps: our personal track, our group members tracks, and the entire class' tracks.

Fig. 8 - My personal track log.

Fig. 9 - Track logs for our group (1).

Fig. 10 - Track logs for all of the groups.

Discussion

This week, our group successfully navigated through a whole course! We were pretty excited about this since last week's exercise was a navigational fail. This week we felt a lot more comfortable with this style of navigation as most of us had some prior familiarity with GPS navigation. We felt that this style of navigation was way more effective than using compass and map. We were the first group to finish, I believe and within 2 hours on top of that. Just by looking at Fig. 9 above, it is clear that we never really strayed off track at any point of the course. The only hitch we really had was between point 4a and 5a but that was because the dense forest made us change our path vs. being able to navigate in a straight line through the woods. Also, we wanted to be able to follow the road as long as possible since it was easier traveling. Looking at Fig. 10, it looks that every group did a really good job of navigating through their courses as well. Nobody really went too far off track which is really encouraging to see. I think that this shows that the entire class has a good grasp on navigating with a GPS. I think that if we were able to map out our routes from our map and compass navigation exercise, the routes would be all over the place. This proves that a GPS can be a very effective and accurate way to navigate; more so than a map and compass. I wanted to make an animated map of my track log but my GPS unit failed to collect any time data for my points. I am trying to use one of my team members' track log with time data to figure out the animation which would give a really cool graphic of our route.

Navigation with Map and Compass

Introduction

On Monday, March 4th, we conducted our field navigation exercise at The Priory in Eau Claire, WI as mentioned in last week's post. The weather was overcast as we set out to the field around 3:00 PM with a slight drizzle on and off. Upon arrival, we found our respective group members and gathered inside of the building for a quick briefing on the flag locations where we were to navigate to as well as the equipment we would be allowed to use, a compass and our map. The property was large enough to accomodate 3 different courses, each containing 5 flags so that no two teams would be going the same way and thus making each time navigate alone. The courses were overlapped in areas though on purpose to add an extra challenge to make sure that if a flag was spotted from afar, it was not certain that the flag belonged to the course being navigated but could belong to a different course. This was done to ensure that we were following our compasses because a compass never lies, we were told over and over again.

Methodology

Once we were all gathered in the building, we were handed our printed off maps that we created the week before. In addition, we were given the locations of the flags for the course we were to navigate to in the form of UTM coordinates as shown in Fig. 1.


Fig. 1
 

This figure indicates the course number with the respective flag locations as well as the starting point for each course as well. My group was assigned to Course #1. Once we had this information, we started to plot out all the points on the map as well as noting the azimuth for each one based on the previous point. In Fig. 2, everyone is busy plotting their points on their own maps.

Fig 2.

We used the UTM grid on our maps to find the location of each flag and also the starting point. This took some time as we had to double check our map readings and actually ended up plotting 2 points wrong originally so it is definitely crucial to double check or have someone else on your team take a look to get a second set of eyes to ensure accuracy. This could have been very costly and detrimental to our navigation sesssion if we had not caught these mistakes. Figures 3, 4, and 5 depict our team members plotting the points on our maps.

Fig. 3

Fig. 4

Fig. 5

After we finally got all the points in their right locations, we were taught how a compass works and the appropriate way to utilize it. This website does a good job describing how to use a compass along with good graphical instructions as well: http://www.learn-orienteering.org/old/. Each team member was issued a compass so that everyone got practice in understanding and using one. Obviously, it is extremely important to know how a compass works but it is also necessary to be able to get an azimuth from one point to another, using a compass and map. An azimuth is a directional reading based on a circle where 0° or 365° is north and 180° is south, 90° is east, and 270° is west. This sort of preparation is paramount before going out in the field and trying to figure it out there by trial and error. An azimuth was collected from the starting point to the first flag location and then from the first flag location the second location etc...Once out in the field we need this azimuth to determine in which direction to walk. We could estimate the distance to each point by counting the number of grid cells between each point since each grid cell is 20m x 20m. An estimate of distance is very helpful when navigating so one doesn't wander too far. Figures 6, 7, and 8 depict the process of plotting points on a map and then calculating an azimuth based off of a straight line between points. Also, in Fig. 7 and 8, the elevation range is shown which clued us in to the range of elevation we would experience in locating the flags.

Fig. 6

Fig. 7

Fig. 8

Once we had all of the prep work done for the activity, which took around an hour, we headed outside to the starting point for our course. From there it was just us with a map and compass and the wilderness which is shown in Fig. 9.

Fig. 9

 The snow was still pretty deep throughout the woods and it became readily apparant that I should have worn boots instead of shoes. Anyways, this is basically what we had to navigate through, along with challenging elevation changes. Once at the starting point, we assigned one person to man the map and stay at the starting point, another person to walk a distance in the azimuth direction to a landmark (usually a tree), and then the third person to count paces from the point to where the second person was standing. We thought this would be the most effective way to stay on the right track because it is very easy to get off the correct path when there are trees in your way. Also, we applied the pace count we took the week before to get an estimate how many meters we had walked so that we had a general idea of how close we should be to the flag. Once again, this was not super accurate because we could not walk in a straight line as we had done in the control experiment but was still very helpful we found out. Navigation to the first point went fairly smoothly even though we had to descend a pretty steep incline to reach it. Figure 10 shows a bit of our navigation to the first point. Here I am counting paces between where my partner Beatriz is standing, pointing out the azimuth and where my other partner Kent is, a landmark along the azimuth.


Fig. 10

Fig. 11 depicting more pace counting between Beatriz and Kent

Fig. 12 - Getting deeper into the thicket, suppressing quick navigation.

We were not able to move very quickly through the forest due to the abundance of trees and the deep snow. However, we managed to stay relatively close to the azimuth and only ended up 11 paces to the west of where the flag was. Needless to say, we were pretty pumped and group morale was at an all time high.

Fig. 13 - The flag from where we first spotted it.

Fig. 14 - Kent (left) and I celebrating our find! Great success!

Fig. 15 - False Flag (tree marker)

Morale was soon to take a hit while navigating to the second flag however. To get to the second flag, we had to descend further down into the valley, and a little further than we had to travel from starting point to flag #1. We applied the same strategy as we had done for the first point as it worked out very well for us. At this point, it should be mentioned that my feet were completely soaked and cold, but I continued on. We walked the distance that we felt we needed to go, but saw no flag anywhere so we walked further until we got to a deep ravine. Still, nothing. Beatriz and myself decided to stay at the point where we felt the azimuth and distance were correct and sent Kent out to explore the perimeter. After a time, Kent came back stating that he did not see anything. We then split up and walked all around the area near the ravine since that is where it looked like it should be on our contour map. We ended up wandering around for a good half hour before we decided that maybe we should go back to flag #1 and start over in case we miscalculated the azimuth. At this point, Martin the field supervisor, came by and told us we should look at the bottom of the ravine. We went to the same spot that we originally thought it would be and looked down to the bottom of a very steep ravine, and sure enough, the flag was pretty much at the bottom of the ravine. Here we learned a valuable lesson: always trust your compass. All we failed to do was look all the way down.

Fig. 19 - Point 3 (flag #2) shown atop elevation contours.

At this point, it was getting dark so Martin instructed us to follow him around to the rest of the points so that we could complete the course before it got dark. We did this and then got back to base camp around 6 pm. It turned out that our group and another were the only ones not to finish our course. This was very disappointing to hear. We had the rest of the week to reflect on our outing and figure out what went wrong and why.

Discussion

We all learned a great deal about navigation with a compass and map from the field outing. We started off strong with our navigation exercise, but failed to complete the course after just finding one flag which was very frustrating. One of the issues that was brought up between our group was that we had not really observed the elevation changes too well on our maps which caught us off-gaurd once in the field. Our maps should have shown more detail with the elevation so that it would have been a bit more obvious that flag #2 was far down a ravine. In Fig. 19, the contour lines are 2m intervals, but we should have gone finer detail with the contours. We were following the correct line, but just failed to realize that the flag was all the way down the ravine, not near the edge where it looks like it is on our maps. I blame myself for not using finer contour lines as well as not breaking up the DEM elevations into more classes which led to over generalization of the elevations. Another thing, as mentioned above, is to never second guess your compass. We doubted our compass because we did not see the flag at first, which led us to wander around aimlessly in the woods with the slim hopes of getting lucky and blindly running across the flag. Next time I need to be more prepared for the physical elements of the field by wearing boots and not shoes. Being unprepared for such elements can greatly hinder effective navigation and could also prove to be fatal if alone in the cold. Our method of navigation was very effective though, with each person assigned a different task to keep everyone on track. It is a bit burdensome trying to manage a compass on top of a paper map in the field, but it can be extremely effective though if that is one's only option. Given another shot at the course, we are very confident that we could find all of the flags. I was pretty excited to be able to navigate with a compass though, since I had never done this before. It is a very valuable skill to learn and actually quite simple once one is able to apply it to a field setting. This week, we will be out in the same area doing navigation with a GPS, using lat./long. coordinates instead of UTM



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Field Navigation Map

Introduction
This week's assignment is preparing the class for a field navigation outing at the University's new daycare center, a few miles south of campus, denoted by the place marker here in Fig. 1.

Fig. 1

The total land area that this exercise will take place on is approximately 112 acres in size and consists of hilly and woody terrain. A high resolution aerial image is shown in Fig. 2 with a red boundary box denoting the area in which various points will be placed for the class to navigate to.


Fig. 2

For this exercise, we won't have any fancy navigational instruments such as a GPS, but rather we will be relying on the old school technique of map and compass to find various points scattered around the plot of land. Often times, a GPS might lose it's signal if one is in dense vegetation or maybe the batteries will run out when in the field. Then what? It is vital to be able to navigate without reliance on technology. Knowing how to use a map and compass is a fail proof way to ensure that if in a sticky situation when technology fails, one can find their way to any point on the map. Teams will be split up into teams of three, so once in the field, one person will be walking, the second person navigationg the walker, and the third person manning the compass and map. Each member of the group is responsible for creating a map (front and back) on an 11" x 17" piece of paper. Out of the three, we will agree on which one we will use for the field navigation exercise.

Methodology
The first thing we did in preparation for the navigation exercise was to go outside and conduct a pace count. Essentially, a pace count is a way to count how many steps one takes in a 100 meter stretch. This will become extremely helpful since we won't have a GPS unit to establish an exact distance for us. It should be noted that we conducted the pace count on a sidewalk to get a true 100 meter distance. However, it is also apparent that once in the woods, we won't be able to walk in a straight line, therefore we will have to add a few paces to our own pace counts to adjust to the situation we will face in the woods. Everyone did the pace count at least twice so that we could average our paces if they were off each time we did it. My personal pace count was 67 paces per 100 meters. Also, the reason that we did this exercise in meters is because our maps will utilize a UTM coordinate system which also measures distances in meters.

That being said, let's talk coordinate systems for a bit! Coordinate systems are the single most important part of making a map. One must know which coordinate system is best suited for their area of interest or else the map could become useless or even work against you. Most people are familiar with the standard latidude/longitude coordinate systems, but rarely should this coordinate system be used outside of making a small geographic scale or global map. This is because latitude and longitude cannot be used to measure precise distances which are needed in a navigation situation. Thus, for surveying or navigation uses, a coordinate system suited for a large geographic scale are necessary. The most popular and useful are UTM and State Plane coordinate systems which allow meter precision. A UTM coordinate system breaks the world into longitudinal based strips or zones in order to minimize distortion. More information on UTM coordinate systems can be found here: http://egsc.usgs.gov/isb/pubs/factsheets/fs07701.html.
A State Plane System is a coordinate system developed specifically for each state. The only problem with this is that this system is still considered to broad for an area like the one we will be doing our field activity on. A State Plane system is best suited for an area covering most of a state or an area falling between two UTM zones within a state. We decided that utilizing a UTM coordinate system would suit us best for our exercise. The exercise area falls into UTM zone 15 and we will use the NAD83 datum for reference.

The next step was to compile all of the data we will be using for making our map into a file geodatabase in ArcMap so that we could run the Arctools and spatial analysis tools on the files. Our geodatabse consists of: shapefiles for navigation and point boundaries, orthoimagery of the area of interest, surveyed 2 ft. contour lines, and also a DEM. After getting all of the data into the geodatabase, it is necessary to get all of the data into the same projection so that further analysis can be done accurately. Once again, we wanted to get all of the data into the UTM 15N projection. This is where we hit a bit of a speed bump with the surveyed contour data. This data was in a CAD format and lacked any spatial projection reference as shown in Fig. 3.



Fig. 3

 

 

 

We were unable to succesfully define a projection for this dataset, so we had to follow a specific order of adding layers. First, we had to add our projected orthoimage which then set the data frame projection to UTM 15N so that if any more layers are added, they are automatically projected on the fly to UTM 15N. This does not mean that the projection is defined or changed for the CAD file however, it just allows the dataset to overlay where it should if it had a defined projection of UTM 15N. This is a really nice feature of ArcMap. It is suggested though that even though a dataset lacking projection properties that is projected on the fly, one cannot do any further analysis until the projections are the same in the properties window. To avoid this headache, our group decided that we did not really need to use 2 ft. contour intervals, so we scrapped that dataset. What we did instead was use the DEM and run a spatial analyst tool to make contours set at whatever interval we wanted. We chose to use 2 meter intervals because this size interval will still give us elevation detail but not clutter the map up so much. Fig. 4 shows how cluttered the 2 ft. contour intervals would have made the map. 

Fig. 4

Since the elevation range in this area is from 245m - 312m, it is really not necessary for our purposes to have this detailed of contour lines because it just makes the map more confusing and busy which will distract from effective navigation. All of the various datasets were clipped to fit the Navigation Boundary box so that there was no extra, unneeded data showing.

The map that I made, which was chosen for the group map, is detailed in the following paragraph and images.
For the one side of the map (Fig. 5), I wanted just a basic, clean map showing the contour lines along with the prominent man-made features of the landscape: the Children's Center, two houses in the SW, and a holding pond to the NE highlighted in orange. The purple contour lines are the 2m contours and the green contours are 5m contour lines. I was also able to label each contour line for quick reference. The Children's Center building sits atop the highest elevation point. The inside red square box indicates the point boundary and the outer, thicker red box indicates the navigation boundary. We included a 20m x 20m grid over the top of the map elements so measuring distances will be very easy. Other map elements include: North arrow for reference, scale in meters, and also projection information. 



Fig. 5

On the other side (Fig. 6), I chose to include the orthoimage which will be very helpful for visual reference of the landscape and also a color coded DEM to show the altering elevations of the landscape.

Fig. 6

I left the grid on top as well and then labeled both ends of the elevation legend bar which is incremented into 10m segments. The red areas are the highest elevation and the dark green are the lowest elevations. The goal was to keep the maps simple yet effective and I think that these maps meet the criteria and will be very useful in the field for navigation.

Discussion
The key concepts from this exercise include datasets, map projections, and map elements. All three are extremely important as they each contribute vital information to the map itself and also to the user. One has to decide on what datasets are most important to the map reader and then how to manipulate the datasets to show what you want as well as to create an aesthetically pleasing and useful map. Once again, projections make or break a map. Firstly, make sure to pick an appropriate coordinate system and then make sure all of the datasets are defined to the same projection to provide an accurate range of data. Map elements such as a north arrow, scale, and some sort of legend are also vital elements of map. Without these elements the map becomes very ambigous and useless. These maps will be put to the true test this coming week as we will actually be out in the field implementing them. I just hope these maps work well or my group may start a mutiny against me!