University of California, Riverside

UCR GeoPad Digital Field Mapping System



Research Implementation


Research

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My Approach

Research-Grade GPS Positioning

Tethering a GeoPad to a Cell Phone

Theodolite for Surface Exposure Dating

Post-Export Data Manipulation

Google Earth
ArcGIS
Move
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My Approach

 

When teaching students I emphasize the need to create clear and careful notes while in the field and the importance of producing crisp linework that is tidy (it is what they are expected to turn in and are graded on). However, the reality is that my opportunities for fieldwork are so few and far between, and often can involve such hard-to-get-to locations, that efficiency is of greatest importance. For me a well-utilized hour in the field is worth ten staring at a computer screen in my office...for better or worse this means staring at a computer screen while in the field too! These days I do all field mapping and most structural measurements using a GeoPad, as well as brief notes, low priority field photos, and some field sketches. I back up important GPS locations in my paper field notebook and still use it for more involved descriptions or sketches. I always take a digital SLR camera for important photos where the greatest manual control and resolution are crucial. Two other useful tips: (1) I always make sure the time on my phone, GeoPad, camera, GPS, and all other recording electronic devices are perfectly synced so that it is foolproof to correlate times and locations outside of the field. (2) Recording a GPS track all day (takes little battery on a Bad Elf GPS) provides an important backup record of where you were and when, which again can help reconstruct locations of photos and samples taken. Once out of the field I export the field data (mapping, measurements, geotagged notes, etc.) primarily to ArcGIS for further editing and geospatial analysis.

I will aim to add more topics and content with time, but for now I have included a few research-based uses of the GeoPads beyond what is perhaps useful to teach undergraduate students.

Research-Grade GPS Positioning

 

Cell phones and other consumer-grade GPSs (~3-10 m positional accuracy) are usually sufficiently accurate for student mapping projects, but research applications can demand greater accuracy such as mapping-grade GPS (~1 m accuracy) or survey-grade GPS (~1-10 cm accuracy = $$$ & considerable weight). FieldMove allows for 6 decimal places for its latitudinal and longitudinal measurements, meaning that depending on your latitude it is capable of recording horizontal position to within 11 cm (and vertical positioning to 1 m), sufficient for most field applications other than surveying. To achieve accuracy beyond that you would have to store the positional data outside of FieldMove.


While you could use an external Trimble GPS and manually override the location, the Bad Elf GNSS Surveyor (discussed above) is a handy bluetooth GPS that interfaces very effectively with iPads. This opens up an option to achieve 1 m accuracy in-field by connecting to an NTRIP feed for real-time differential GPS corrections, or to record raw satellite data (as a RINEX file) to enable later post-processing of important locations. With a location occupation time of 10-15 minutes it is possible to post-process for 20-50 cm accuracy with a Bad Elf. So far I have trialed the California Real Time Network (no success) and UNAVCO's real-time GPS data broadcast.

Below are some resources to get you started:

https://bad-elf.com/blogs/bad-elf/announcement-bad-elf-supports-high-accuracy-location-in-esri-collector

https://bad-elf.com/blogs/bad-elf/announcement-new-bad-elf-app-and-firmware-for-the-gnss-surveyor-accessory-post-processing-and-dgps-support

https://bad-elf.com/pages/post-processing-gnss-data-with-rtklib-introduction

http://www.unavco.org/data/gps-gnss/real-time/real-time.html

Tethering a GeoPad to a Cell Phone

 

Few people (academics at least) will want to buy a dedicated phone and data service plan for their GeoPads but it is possible to "tether" the GeoPad to a smartphone that has coverage and is supported. Essentially this consists of using your phone as a personal internet hotspot by linking it remotely to your iPad by wifi or bluetooth connection. I would consider this one step too far for teaching uses but for researchers it has benefits. The main advantages are in-field access to online imagery (for example provided by FieldMove and GaiaGPS) and the ability to connect to a real-time NTRIP feed to obtain in-field GPS position accuracy of 1 m with a Bad Elf GNSS Surveyor (see above). A Google search should pull in specific information on hotspot tethering for your make of phone and service provider.

Theodolite for Surface Exposure Dating

 

Although far from its intended use, I have found that the Theodolite app is perfectly designed to efficiently record and calculate topographic shielding when collecting samples for cosmogenic surface exposure dating (an important technique in geomorphology). The important measurements are the inclination of the horizon at 15-45 degree increments and the approximate position and altitude, which allow calculation of the cosmic ray shielding factor crucial for exposure age determination. Theodolite overlays all this necessary data onto a photo! Just point the crosshairs at the horizon and press the save button. In contrast to the time-consuming analog method of recording bearings by compass and inclinometer, the images reliably preserve the horizon angle, azimuth, GPS location, altitude, and date, as well as providing a complete visual context for the collected sample (useful to document stability of the site, potential for fires, man-made disturbances, etc.). In about two minutes I can complete the necessary field measurements that would traditionally have taken me closer to ten or fifteen minutes. Bonus tip: I will use this program's calibration tools if the compass measurements seem to be acting up in FieldMove.


Two examples of images saved from Theodolite: quick and accurate sightings
theo

theo2

Post-Export Data Manipulation

Google Earth

 

As discussed on the Teaching page, exporting your field data to Google Earth (.kmz) is the quickest and easiest way to view, edit, and share data. From my experience the files can cause Google Earth to crash and so having it backed up in another format is wise.

ArcGIS

 

Google Earth may be a useful stopping point for many undergraduate student projects but graduate students or other researchers may wish to push their field data to ArcGIS or other GIS softwares (GRASS & QGIS for free open-source options). Using the Export feature in FieldMove you can push data to ArcGIS in two ways:

 

(1) Convert the exported .kmz file (best for bulk import of data)

(2) Convert the exported .csv files (best if you want to separate out point, line, polygon, planar measurements, note data, etc.)

Move


The third Export option is a .mve file. I have only just begun to experiment with “moving” data from FieldMove to Move, but this is essentially what FieldMove was designed to do. Move is a full feature structural geology software suite allowing the creation of geologically valid 2D/3D kinematic models and cross sections, fault slip analyses, stress analyses, etc. I will share my experiences with Move as they develop.

For an overview of the software visit Midland Valley's website:

https://www.mve.com/software/move

To promote its use, Midland Valley currently offers free academic licenses for Move:
www.mve.com/filemanager/images/software/2014/.../Move2014.2_LicensingGuide.pdf

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More Information 

General Campus Information

University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

Contact Information

UCR GeoPad Digital Field Mapping System
Department of Earth Sciences

Tel: (951) 827-3183
E-mail: nic.barth@ucr.edu

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