Posts Tagged ‘iupui’

To test the feasibility of a low cost, mobile environmental sensor system that could be used to sample air quality as needed and in areas where conventional sensor systems may not be available or cost effective.

Based around the low-cost Arduino microcontroller, a GPS shield for capturing geographic location was paired with a relative humidity and temperature sensor to act as a mobile data logger. The relative humidity and temperature sensors were chosen for their cost and ease of implementation as an initial set of sensors. The sensors were mounted at the end of a five foot long section of one-inch PVC mast inside a one-inch to two inch tee fitting. The tee fitting was used to protect the sensors from direct sunlight and weather (Figure 1).


Figure 1

The entire unit is powered by a single 9-volt alkaline battery and housed inside a rigid plastic storage container to protect the equipment from handling and the elements. The 9-volt battery should power the unit for several hours and a 9-volt lithium may provide even more operating time (Figure 2).


Figure 2

Software was modified based on that supplied by Adafruit industries, the makers and suppliers of the sensors and GPS unit. The software reads the raw GPS datastream and parses out the $GPRMC string, reads the relative humidity and temperature sensor, then writes these values as a line to a comma separated value text file on a microSD card on the GPS shield. Each additional reading from the time the unit is started is appended to this text file. If power is interrupted to the unit, when it restarts it will create a new file before appending data.

For the initial test of the unit, it was placed inside a backpack with the mast rising to approximately seven feet above the ground. The trip was made on a standard mountain bike and ridden at a nominal pace. The initial test site chosen was a road that runs from north to south from West Walnut Street in Greencastle, IN to the DePauw Nature Park parking lot. There is a change in elevation of roughly fifteen feet where the road enters the forest area at the north end. Otherwise the road is nearly level throughout. The distance covered was approximately 1.7 miles roundtrip and the sensor unit gathered 1059 data points during this trip. Riding was done by staying as close as comfortable to the outside edges of the road for not only safety reasons, but to also help determine the accuracy of the GPS unit.

The unit was turned on and allowed to get a fix on the satellite constellation, then an additional five minutes was allowed to elapse to allow the sensors to acclimate to ambient conditions. Upon return to starting position, the unit was turned off and the file from the microSD card removed and the file copied off.

The data file was opened in Microsoft Excel and the GPRMC latitude and longitude coordinates converted to decimal degrees for use in the GIS. This was done by extracting the degree portion of the latitude string, dividing the rest of the string by 60, then adding the two back together. The temperature was also converted from degrees Celsius to degrees Fahrenheit using the standard formula. Table 1 shows a sample of the raw data file collected and Table 2 shows a sample of the finished spreadsheet.


The resulting Microsoft Excel table was then opened in ArcGIS 10.1 and the XY data used to plot the points (Figure 3).


Figure 3

The projection used by the GPS constellation is WAS 1984 and that was what was used here. A basemap of aerial imagery was then added for reference. Finally, the point data was buffered to 25 meters, the points were kriged, and then the kriged raster was clipped using the buffer (Figure 4).


Figure 4

This project has shown the feasibility of using low cost, mobile arduino-based devices as environmental sensor systems that could be used to sample air quality as needed and in areas where conventional sensor systems may not be available or cost effective.

Several future considerations should be considered, including increasing the number and type of sensors such as adding benzene, NO2, or similar sensors. Additional or different sensors can be added or changed out with minimal effort in programming or hardware.

Another area of interest would be to outfit similar units with small solar panels and battery backup systems so that they could be placed in remote locations, thereby increasing the ability to monitor environmental pollution throughout a much wider area.


#GISDay was a great success this year, at least for me. A chance to renew contacts I made last year, meet new ones and hang out with friends all day. Four of us piled into the truck and headed to Bloomington this morning from IUPUI Campus and descended upon the Wells Library at IU. Compared to last year, there was more energy, more talk, and a lot more going on. The big news is the LiDAR data that is in the final stages of post-processing and will be completed this year. This will be LiDAR coverage of the entire state of Indiana, giving everyone in the geospatial community a never-before-seen resolution and accuracy data set. Projects such as subsidence tracking from old mining sites, public health issues, and forestry applications, both urban and rural, are just a few of the projects overheard or talked about today.

Thanks to my traveling companions for making the trip to and from a lot more interesting, and to all those who took their time to talk with us and share the GIS experience.

Now if I can just scrape together the cash for a trip to the ESRI UC this summer I will be all set . . .

Finally had a chance to make some changes to the site, so here is what’s new.

  • I have started a seperate page for the Putnam County @ Your Feet maps and moved the bedrock layer over to that page. I hope to have a surficial layer map up soon.
  • I am also creating a page for some heat maps and other items I am working on using the 911 call data from Putnam County, Indiana.
  • For my Advanced Remote Sensing class this semester, I am working on identifying Bobcat (Felis rufus) habitat in Southern Indiana. I will post the results of that here at the end of the semester and ask for feedback.

Besides maps, I am also taking a course on Applied Spatial Statistics (go Bayes’ Theorem!) and also data visualization class. Hopefully I can start adding some analysis to the maps and projects soon. As always you can follow my blog (I don’t post much so I won’t be cluttering up your life), also on Twitter (@JeffreyAshby) and on Facebook (jeffrey.ashby1).

The First Post

Posted: October 22, 2012 in Uncategorized
Tags: , , , ,

So to start of this blog dedicated to GIS and Geography, I thought I would toss out a few quotes I stumbled across while sauntering around the Internet.

“Everything has to do with geography.” – Judy Martz

“Geography is important, because it opens our eyes; a landscape is no longer a static feature, but a complex battleground of physical and human interactions. Local is no longer local, but a collision point for the interaction of many ‘locals’ drawn from a global stage. With technology increasingly drawing the world closer together, it is important that the role of Geography in helping the public in understanding this complex and unpredictable world is championed!” – Tony Cassidy

“Anybody who believes that the way to a man’s heart is through his stomach flunked geography.” – Robert Byrne

“If geography is prose, maps are iconography.” – Lennart Meri

Ok, that’s enough for now. I plan on posting about projects I work on, modified versions of assignments for classes, stuff I do for fun, and any other geographic and GIS items that come across my desktop. Some of it will be informational, so whimsical, and some tutorial. If you want to know more, check out the About Got GIS? And Jeffrey Ashby page for more.

I am currently looking for a job in the GIS field, so would appreciate your help in finding one. Preferably in the Indianapolis, Indiana area, or Central Indiana, or the United Kingdom, or Sweden, any of those areas are good.

I am a member of the Association of American Geographers and Golden Key International Honour Society. While most of what I do and show will be using programs like ArcGIS and ERDAS Imagine or Exelis ENVI, I may also delve into some of the open source programs like QGIS and Multispec.

Geography is fascinating to me, the where of it all, but with the tools available today we can use a combination of GIS and Remote Sensing to understand our world far better than at any other time. From knowing how well the crops are doing in the fields (and what is being grown there) with space based imaging systems, to knowing who will be affected if a dam should break. It is an exciting time and I can only see it getting better.

Did I say check out the About page? Get over there and look at some of the cool things I have done, then drop me a note at