When a meteorite fall occurs, meteor hunters often simply grab a map, a GPS, and head for the fall. While this works, there is a better way to plan an expedition using GIS (Geographic Information System) software. Using open source software, free government data available online, and a few hours, these meteor hunters will know a lot more before they get to the meteor fall. This, in turn, will increase the number of recovered meteorite fragments and reduce the cost in terms of money, time and effort invested.

GIS is software that takes information with a geographic component and displays it on a map. Like lines that show where rivers and streams are, or dots that show individual cases of West Nile virus. Each line or data point can be queried to get more information about the data record, such as name, flow and depth of a river or name, hospital, age, etc. of a patient with West Nile virus. Essentially a georeferenced database. Each database of information is called a layer. You can easily get free layers of hydrology, cropland use, rainfall measurements, soil type, acreage property parcels, and many cultural datasets. Each and every layer will be stacked on top of the basemap layer to give a representation of the land. Any particular layer can be made invisible or translucent to make other layers more apparent.

There are a variety of GIS programs available, the most common being ESRI’s ArcView, but it costs $1,600 per seat and is overkill for the meteorologist’s needs. A better solution is open source programs like Quantum GIS or gvSIG. Both are free, full-featured GIS programs and can perform spatial analysis. Quantum GIS is recommended at this time as it is free, easy to learn, intuitive to use, and quick to represent data sets even on older laptops. Download a copy at Qgis.org. All GIS programs will benefit from a good video card and more RAM.

Google Earth is a low-grade non-GIS mapping tool. It allows you to drop point layers, but the free version will not read other data layers or perform any spatial analysis. Also, it will not allow you to print large maps. This is a big drawback. Ironically, non-GIS users think it’s great, but it’s a toy compared to real GIS programs.

The immediate GIS needs of the meteor hunter will come down to two critical questions:

a) Where is the sown field? Y
b) How is the field sown?

To satisfy these needs, it is necessary to obtain some data layers. The first will be the basemap layer. A basemap is the important reference layer on which all other layers are built. For a Texas project, the base map would be the outline of the state of Texas, satellite imagery, or the full topographic map of the state of Texas. Any basemap that makes sense to you is correct. Since the average meteor fall should be less than a 30 km x 30 km area, I recommend using a topographic map as a base map.

Now that a basemap has been chosen, we need more data layers to help with the search:

-Main Highways
-Minor Roads
-Private Roads
-Railways
-All hydrology, lakes, rivers, streams, etc.
-Cropland Designations
-Satellite photos (you want to see buildings for reference)
-Denominations of vegetation
-Cadastral data (Polygons of surface property that contain names of owners)
-Soil type
-Topography

Most of these should be available online from some government agency for free or for a reasonable charge. Some may not be, but as long as you have the majority, you’ll be ahead of the game. Each layer has a use for the meteor hunter, and I’ll describe each use here.

Highways, main, secondary and private, along with railways, are important on three levels. First, if the drop was in a remote area, this layer will tell you how close you can get to the target in a wheeled vehicle. Second, this layer may be more up-to-date than the maps you have available, so you may find you can drive to the target when maps published 10 years ago say you have to walk the last 5km. Third, in the US and some countries, meteorites found on public roads and in your right of way are easy prey for anyone. Private roads will require permission to hunt, but it’s good to know which is which.

Hydrology becomes important in remote places. Knowing stream names and reference field notes with hydrological characteristics may be helpful. For ancient falls, such as the Deport iron meteorites, I found that within 20 meters of the streams, the irons were buried more deeply due to presumably flood sediments. In the case of the Ash Creek Fall in the City of West, Texas, hydrology simply helped define boundaries and property lines that were not seen on published maps.

Farmland data is great for knowing where to start your search as soon as you get there. Before you go, you can know that in April, the northern half of the sown field must be cornfields. It may be that there are fallow areas to the south. Once the meteor hunter arrives on the scene, farmland data confirmation will be needed. For ancient finds, meteor hunters might focus on talking to farms of a specific type, such as cotton, which tend to be more disturbed soil than other crops. I have used this in my ninja exploration of some areas in West Texas to retrieve various meteorites.

Satellite photos are great in many ways. First, it gives you the size of a parcel of land based on the color of the ground cover. In the US, a ‘section’ of land is 1 square mile, which is 640 acres. An aerial photo may show 5 parcels in that section, suggesting you may only need to get permission from 5 people to hunt. The photos also show areas that are wooded or have other plant cues that indicate good or poor hunting areas.

Vegetation designation is different from Cropland in that it must cover the entire area and not just agricultural areas. I could tell you that the vast majority of the ground is covered in 2 centimeters of moss, which is terrible. As it was for us hunting for an old drop in Stelldaellen, Sweden, but great for a new drop. Bad hunting areas such as marshy and swampy areas can be identified in advance, which will improve hunting by not wasting time in these poor areas and shifting hunting effort to areas indicated as higher ground with sparse vegetation.

Surface owner parcels are the same as real estate parcels. Basically, these are proprietary land form polygons. This can be a difficult layer to obtain, but it is quite useful. You will know who owns the land and you will be able to make phone calls without having to knock on a tenant or tenant’s door and get the name of the owner. This layer will save the meteor hunter a great deal of time finding facts in the field. Remember, the landlord can give you permission to hunt the land and keep the meteorites found, not the tenant.

Ground type layers are most useful with old drops and hunts after older finds. Had this layer been available to me on an expedition to Karatu, Tanzania, it would have aborted that goal. This is because when I got to the area of ​​the Karatu fall I found that the area was volcanic with black rocks with a ferrous component and I was looking for stones from a 40 year old fall. It was terrible terrain to try to hunt, and nearly impossible to train the locals to tell a meteor from a wrong meteor. Most US states have good soil type maps.

Once the meteor hunter is on site, there are two layers that will need to be created. First, there is a point layer that will be the location of all meteorite finds. This will be necessary to start seeing trends and establishing a stray field direction line. The second layer will be a polygon layer that will show the areas that have been searched and reduce duplication of effort. With this layer, it will be helpful for the meteor hunter to use visible landmarks that can be seen from the topo layer or aerial photography to start and stop their search areas. In the case of the Deport iron hunt, I used telephone poles and the edges of agricultural fields as reference points because they appeared on 1m resolution aerial photographs.

These layers can be obtained from many sources. I discovered that the source of the best and most accurate data is at the lowest level of government. In the case of Ash Creek, Texas, the 1m resolution satellite imagery came from TNRIS (Texas Natural Resources Information System), the topology from a CD product I owned, and the land cover came from another state agency. Of course, I had to ask the local meteorite hunters where they had found stones and their size. This gave me the most definitive map on the fall of Ash Creek that is known to exist. I continued to find 8 stones weighing in at half a kilo.

In short, GIS should be in every meteor hunter’s toolbox along with their magnet, walking stick, hat, Doppler radar, water bottles, and hiking boots. It’s the tool that will preselect good terrain from bad to optimize the little time you have on a fall. On site, it can be used to better track known finds to clean up the scattered field. Additionally, it should be used to quickly and efficiently identify surface owners to contact for permits.

Good luck and good hunting!