Activity 1: Creating a Coordinate System

Introduction

The goal of this activity was to create a coordinate system to evaluate a land surface in order to create a digital elevation model in later exercises. Creating coordinate systems and elevation models are used by people studying a range of different topics including bathymetry and island coastal mapping for planning safe entry and exit points for seafarers. We began this exercise by creating our own landscape within a 122cm x 125cm wooden box. We needed our landscape to contain a variety of landforms to practice accurately measuring differential elevations. For this reason, our landscape contained 2 hills, a valley, a ridge, a depression, and a plain.

Study area

We began our study within a sandy region of the floodplain of the Chippewa River on Friday, September  18. The study area was limited to the area inside our 122cm x 125cm wooden box. The study took place from 1:00pm-4:30pm. The weather was overall cloudy and dry, however, there was a slight sprinkle towards the later portion of the activity.

Methods

We began by laying down our 122cm x 125cm box in a relatively level portion of sandy floodplain. We then used a level to make sure both the wooden box and the sand within it was level to assure accurate elevation measurements.

Fig. 1: Our finished sculpted study area containing all land
features: hills, a valley, a ridge, and a depression.

Creating our Terrain

We then sculpted our terrain within the box to contain all of the landscape elements previously mentioned (2 hills, a valley, a ridge, a depression, and a plain).

Fig 2: The finished 8cm x 8cm grid created by wrapping
string around tacks set at the desired interval.

Setting up a Coordinate System

After sculpting our landscape, we divided the area into 8 cm x 8 cm squares using string thread around tacks placed on the wooden rim of the box at these set intervals. We labeled our coordinate system as X1, 2, 3, etc..., and Y1, 2, 3, etc... on either side of the wooden box edge.

Fig 3: Students (Ally Hillstrom and Casey Aumann) gathering
and recording elevation measurements

Our Z coordinate was measured as the depth  from the surface of the box to the sand surface beneath it and thus recorded in negative values. 

Fig 4: A sample of 25 points within the data recorded on excel.

Data Collection

The data was collected from the upper right-hand corner of each 8cm x 8 cm square using a meter stick and all depths were measured in centimeters. A total of 201 values were collected and entered into an excel spread sheet. 

Discussion

This activity allowed us to engage our critical thinking skills and gain a better understanding of how to create a coordinate system and elevation model.  Some difficulties we had during this project was deciding upon where to designate sea level, or z-value of "0cm." We decided to make "0cm" flesh with the top of our wooden box because it allowed us to make accurate measurements as it eliminated any error that may have existed in leveling the sand within the box before sculpting. We also had difficulty deciding how large to make the grid squares of the x- and y- coordinates as the length and width of the study area was irregular and the box corners were held together by pieces of wood from the inside of the study area, making an inconsistent study area shape. We eventually decided to make the squares 8cm x 8cm because we felt it would allow for enough measurements to make an accurate digital elevation model without having too many measurements. We also decided any fraction of an 8cm x 8cm square would not be included within the measurements. This made data collection consistent, but did negate portions of total study area. It would be interesting to see how other groups dealt with this problem of an irregular study area.

Conclusion

In conclusion, this activity did help us to develop a better understanding for the processes that occur behind developing coordinate systems and elevation models. Because we were given no instructions on how to gather data, we had to use our critical thinking skills to develop our own methods.