Initial Publication Date: April 24, 2018

Instructor Materials: Overview of the High Precision Positioning module

Module Goals

Students will be able to:

Design and conduct static and/or kinematic GPS/GNSS surveys to address a geologic research question.
Apply the findings of GPS/GNSS surveys to issues important to society
Justify why different high-precision positioning techniques are appropriate in different situations.

Show more info on how Module Goals connect to science literacy principles

Summative Assessment

The overarching Summative Assessment for the module is a series of critical thinking questions that ask students to synthesize learning across the different units. Instructors may elect to use some of these questions for final exams or other final assessments. In addition, each unit includes important summative assessment questions for topics and concepts specific to that unit. These are also critical because there is a high probability that most teachers will only teach a subset of the units. The assessment questions are broad because each instructor will use a different field setting. Remote field teaching ideas and prepared data sets are available for those courses who are unable to collect their own field data. Pre-existing data sets are available to help locate interesting change detection options. Learn more about assessing student learning in this module.

Outline

This module is composed of three core components. The first is an introduction to satellite positioning fundamentals and provides students with the terminology and basic physics to understand how the system works (Unit 1: GPS/GNSS Fundamentals). The second focuses on how kinematic systems work as well as how to create a topographic data set and detect change in monumented positions (Unit 2: Kinematic GPS/GNSS Methods). Unit 2 contains subunits that introduce students to specific applications for using kinematic GPS/GNSS: topographic surveys and change detection. Unit 3 is an exploration of static systems, which provide the highest precision necessary for detecting extremely small changes (Unit 3: Static GPS/GNSS Methods).

The module introduces material in an order of increasing complexity and precision, but the units (after Unit 1) can often be taught as stand-alone lessons. For instructors who do not wish to use the module in its entirety, suggested pairings are included in the "Context for Use" section on each unit's page. Instructors can request support for some types of equipment and technical support from UNAVCO, which runs the NSF's Geodetic Facility.

Note: Although the term GPS (Global Positioning System) is more commonly used in everyday language, it officially refers only to the USA's constellation of satellites. GNSS (Global Navigation Satellite System) is a universal term that refers to all satellite navigation systems including those from the USA (GPS), Russia (GLONASS), European Union (Galileo), China (BeiDou), and others. In this module, we use the term GNSS to refer generically to the use of one or more satellite constellations to determine position.

Unit 1GPS/GNSS Fundamentals

This unit introduces students to how global navigation satellite systems work, a comparison of their accuracy and a first field opportunity to set up an antenna and receiver.

The constellations of satellites orbiting our planet enable high-precision positioning not just for consumer or survey applications but also for geoscience research such as detecting plate motions, landslide movement, or other changes on the Earth's surface. This unit introduces students to the fundamentals of these global navigation satellite systems (GNSS), the reference frames used for positioning and the different acquisition techniques, including their merits and accuracy. Through classroom and field activities, students develop a familiarity with the variety of instrumentation and applications available with GNSS. This unit provides a broad conceptual understanding of GNSS applicable to all acquisition techniques. Subsequent units focus on kinematic and static methods and the different products generated using those GNSS methods.

Unit 2Kinematic GPS/GNSS Methods

This unit focuses on teaching the techniques necessary to run a kinematic survey. It is explicitly hands-on, giving students the opportunity to set up, operate, and post-process their data. Though they are less precise, kinematic surveys require more equipment and design considerations than static systems. Kinematic systems have the advantage of rapidly acquiring numerous positions with an accuracy of several cm. They are effective for a variety of applications including measuring rapidly deforming landforms, surveying topography, or other applications that are time sensitive and do not require precision greater than 2–3 cm.

The application of Global Navigation Satellite Systems (GNSS) in the earth sciences has become commonplace. GNSS data can be collected rapidly and compared in common reference frames. Real-time kinematic (RTK) GNSS methods enable the rapid delivery of high-precision, high-accuracy positioning information to field scientists. This unit focuses on the design and execution of kinematic surveys, emphasizing the benefits and limitations of the technique. Students will learn which questions the technique is most applicable for as well as the standard data-processing techniques. Students advance their understanding of GNSS through a technical knowledge of kinematic GNSS surveys. This unit prepares students to design and implement a survey of their own through hands-on instruction and demonstration of real-time kinematic (RTK) or post-processed kinematic (PPK) techniques in a field setting.

~~Unit 2.1~~Measuring Topography with Kinematic GPS/GNSS

This unit focuses on an application of kinematic techniques to rapidly and efficiently collect topographic points and process them to create a continuous surface.

Kinematic GNSS surveys can provide a rapid means of collecting widely distributed, high-precision topographic data. The advantages of this technique over optical instruments such as a total station are that it only requires one person to operate and it does not rely on maintaining a direct line of site. Once points are collected, students will learn to interpolate them using ArcMap to create a continuous model of elevations. Students must think carefully about where they collect their points and evaluate the merits of different interpolation techniques including TIN and Kriging. Through a field-based application of kinematic GNSS, students will design and conduct a topographic survey and interpolate collected points to create a continuous elevation field. This builds upon skills learned in Unit 2 and prepares students for future techniques such as surface differencing and topographic change detection (Unit 2.2).

~~Unit 2.2~~Change Detection with Kinematic GPS/GNSS

This unit focuses on the application of kinematic techniques to detect change in monumented objects such as benchmarks or boulders moving down a hillslope.

Though it may be difficult to perceive, landscapes are constantly changing form and position. High-precision GNSS is one of a handful of techniques capable of quantifying these changes and is a key component of many modern geologic, biologic, and engineering studies. In this unit, students will learn how to approach a study in change detection in the context of a geomorphic or structural problem, then design and implement a GNSS survey that effectively explores the problem. Through field-based application of kinematic GNSS techniques, students will design, execute, and analyze data from a survey to detect change. Students design the survey based on a question of scientific or societal interest and are asked to defend their design and implementation. This is the final unit focused on kinematic GNSS and is aimed at solidifying students' knowledge and technical skill in this technique.

Unit 3Static GPS/GNSS Methods

This unit focuses on teaching the tools and techniques necessary to run a static survey. It is explicitly hands-on, giving students the opportunity to set up, operate, and post-process their data. Static surveys take more time to collect points than a kinematic system, but they can be significantly more precise, able to resolve movements of several millimeters, including hill slope creep, slow-moving landforms, and tectonic motion. Static systems vary depending on application, but are often used for time-series analysis of slow-moving monuments.

The application of Global Navigation Satellite Systems (GNSS) in the earth sciences has become commonplace. GNSS data can produce high-accuracy, high-resolution measurements in common reference frames. Static GNSS methods take advantage of long occupation times to resolve fine measurement and time-series data to capture events such as tectonic deformation, earthquakes, groundwater depletion, and slow-moving landforms. This unit focuses on design and field execution of simple static surveys, emphasizing the benefits and limitations of the technique. Students will learn which applications the technique is most applicable for as well as the standard data-processing techniques. Additionally, students advance their understanding of GNSS systems through interpretation of field data from static surveys and public data sets of continuous-operation stations. This unit prepares students to design and implement a survey of their own through hands-on instruction and demonstration of rapid-static or static techniques in a field setting.

Summative Assessment

There is no single summative assessment for this module. This is because kinematic and static GNSS require different equipment and different interpretative tools. Instead, we offer a suite of questions that may added into the summative exercise of different units. Alternatively, these questions may be asked as part of a final exam.

Making the Module Work

To adapt all or part of the module for your classroom you will also want to read through

Instructor Stories, which detail how the module was adapted for use at different institutions, as well as our guide to
Using GETSI Modules for Your Course, which outlines how to effectively use GETSI modules.

The module authors provided additional information about teaching this module. If interested, click on the blue text below to display these notes.

Show more about instruments and technical support

Instrument and technical support: EarthScope, which runs NSF's Geophysical Facilities, has educational "kits" of GNSS/GPS instruments available for the cost of shipping. See more on this module's Equipment and Support page and the EarthScope Geophysics Field Education page. If you have technical questions, contact education@earthscope.org and we will endeavor to answer them or connect you with someone who can.

Show more about keeping students engaged

Keeping students engaged: The course materials contain significant supporting material written into the assignments so that students have ample explanation for why and how they are to complete each step. Much of this material is or should be covered by lectures. If you plan to lecture on much of the written material in the assignments, consider streamlining the assignments so that students do not get lost in reading the accompanying material.

Show more about keeping students occupied

Keeping students occupied: One of the challenges of integrating these techniques into a course with more than a few students is making sure that students stay engaged and mentally challenged even while they are waiting for their instrument time. While they wait to work with geodetic equipment, there are a series of possible tasks that instructors can assign to help students better understand the components of survey design AND keep them occupied and engaged. These include:

Multiple rovers can operate concurrently from the same base station. Groups of 4 or 5 per rover are a maximum. Alternatively, one set of students can be keeping field notes and filling equipment sheets while the other part of the group is physically navigating the unit.

During surveying, split tasks between individuals in a group, rotating between taking notes, operating the equipment, and/or finding the next point to measure.

On the first day, students should be encouraged to review their geodetic method field manual(s) during any downtime they may have.

Students can complete equipment sheets from their assignment packet for surveys during downtime.

Survey maps and accompanying notes are very important. Remind students to periodically update maps and field notes.

Consider having the students take traditional observations and measurements: strike/dip, rock type, and other observations, which can inform their write-ups later.

Show more about safety in the field

Safety in the field:

Prior to taking students into the field

Instructors should have had a first aid course

Place in every vehicle:

Document of phone numbers for local police and hospitals along with directions/maps to nearby hospitals/emergency medical sites.

List of student allergies

Access to vehicle keys is another issue that needs to be made clear (where and how stored)

Safety equipment needed (helmets, reflective vests, ear protection)

The start of every field day

Begin with a field safety reminder which includes a general schedule for the day, anticipated weather conditions, and any special equipment handling/deployment that will be taking place.

Description of how student recall will be handled if it is necessary to initiate a return to the vehicles for an early departure (e.g. thunderstorm, injury) -- might involve use of an air horn or car horns to signal a return (cell phone might be ok in some areas

As applicable

Stream crossing safety

Barbwire fence safety

Potentially dangerous animal/plant warnings (e.g. poisonous snakes, bears, cattle, poison oak)

Unstable or dangerous areas of the field site (e.g. loose rocks)

Show more about data exploration

More about data exploration:

One limitation of this unit for field courses is the reliance on computers for interpretation and analysis. Computers with necessary programs (ArcMap and post-processing software) should be loaded prior to the course and tested.

An internet connection is necessary for post-processing through systems such as OPUS. Kinematic post-processing can often be done without a connection if using an established benchmark.

Consider surveying points and processing a stable data set ahead of the course if you expect any trouble or are new to the process! Download a prepared dataset (such as provided in several units) in case your survey fails for any reason.

Allow time to post-process! There is a typical 24-hour lag time between when a survey finishes and when OPUS will have stable corrections for that time period. Allow time in the schedule for this to take place or use a pre-processed base station or monument.

Show additional tips

Additional tips:

GNSS surveys are equipment-heavy, so plan accordingly for getting it into the field.

Four or five students is the maximum per rover unit in kinematic surveys. However, you can have as many rovers connected to a base station as you like.

GNSS does not work well in heavy vegetation or urban areas where a significant portion of the sky is obstructed.

Anticipate the survey process moving slowly initially as students become familiar with instrumentation setup and the data-collection workflow.

Visit the site prior to taking students there to survey—to assess access, site size, features and vegetation that may obstruct or complicate the survey, and to obtain landowner permission (if required).

Show more about metacognition

Metacognition (reflection) is built into all student exercises in this module. Metacognition, or "thinking about thinking," encourages students to examine what and how they learned, to help them monitor and then alter their learning techniques to ensure best learning practices. Each unit's final write-up includes a reflection question for students to answer about their learning experience. In addition, ask students questions such as: What was rewarding about this exercise? What was challenging? How have your ideas about fieldwork changed because of your experience with geodetic techniques? What other applications would you suggest applying geodetic techniques to in future research you might do? More information on metacognition is at InTeGrate Project's Metacognition page and Teaching Metacognition by the Cutting Edge Project.

Show more about societal importance

Societal importance: For each of the units, students are also asked to apply findings from the different types of surveys to societally important applications. Research shows that students are more engaged in subject matter they see as relevant and important. By tying what might appear to be dry geophysics methods to the underlying reasons we want to conduct such research, students see the relevance and importance of geoscience in everyday life. Geodetic surveys can be used to answer research questions on disparate topics from earthquake, volcano, and landslide hazards to climate change (ex. glacial study).

Show more about adapting the module to non-field courses