The Value of GPS-Based Field Records

By Tom Doerge and Doug Gardner


  • GPS receivers allow growers to easily collect many types of time- and geo-referenced records for their fields.
  • These GPS-based field records include boundary, soil, crop, topography, as-planted and as-applied maps, scouting reports and additional local features.
  • These records allow growers to manage field scale variability more proactively and be more reactive to unexpected changes in weather or marketing conditions.
  • Specialized GIS software can use GPS-based records to create new kinds of field-specific information that enhance agronomic and enterprise efficiency.
  • Future GPS-based records will add value to specialty-trait grain through enhanced identity-preserved marketing and allow remote, real-time monitoring of equipment, personnel and crop performance.


New positioning, sensor and computer technologies are dramatically changing the way farmers can manage their crops, and their businesses. Prior to personal computers and the Global Positioning System (GPS), growers relied on paper-based record-keeping systems to handle site-specific information for individual farm fields. Today, growers and their employees collect this same information with the aid of an increasing array of precision farming tools such as yield monitors, hand-held logging devices, GPS-equipped four-wheelers, and even wireless Internet equipment. The spatial data collected can then be transformed into maps for immediate use (Anderson, 1999). These data can be further analyzed to create new kinds of information for agronomic and enterprise management. This Crop Insights discusses how GPS-based field records can be used to add value to precision farming operations today and in the future.

What Are GPS-Based Field Records?

GPS-based field records are time- and geo-referenced information that describe a farm field and the activities conducted within that field. Geo-referencing is the use of latitude, longitude and elevation readings from a GPS receiver to place point, line, area, and topographic features within a field at their exact location on the earth's surface.

Almost any kind of data can be included in these field records (see table and figure below). These include boundary, soil, crop, topography, as-planted and as-applied maps, scouting reports and other local geographical features (Peterson and Doerge, 1998).

Photo: Applying anhydrous ammonia with a GPS-equipped tractor.
Applying anhydrous ammonia with a GPS-equipped tractor.

Table 1. Listing of commonly-used time- and geo-referenced information in GPS-based field records.

Data Layer Need for re-sampling (after original measurement)
Field Characteristics  
  • Field boundary
  • NRCS soil survey map
  • Drainage tile lines and outlets
  • Elevation/topography
  • Soil electrical conductivity map
  • Soil test maps (pH, P, K, etc.)
  • Slope and aspect maps
  • Bare soil aerial photos - uncorrected and geo-referenced
  • Roads or waterways
  • Rocky areas
  • Old fence lines
  • Roads, streams, lakes, railroads, etc. (TIGER®* data)
  • Only if modified
  • Only if revised
  • Only if modified
  • None
  • None
  • Every 2-4 years
  • None
  • None
  • None
  • Only if modified
  • None
  • None
Field Operations  
  • As-planted map (including non-Bt refuge areas)
  • As-applied maps (spraying, tillage, fertilizer, etc.)
  • Yield maps
  • Once per crop
  • Once per operation
  • Once per crop
Crop or Scouting Information  
  • Scouting maps (weed, insect, disease problem areas, etc.)
  • Plant population map
  • Crop canopy images (color, color IR, etc.)
  • Crop types in fields surrounding the field of interest
  • As needed
  • Once per season
  • As needed
  • Once per crop

It is often overlooked that GPS output also includes a time stamp. The ability to record the time that certain farming operations were conducted could be extremely valuable. One example is explaining final yield variation on a yield map in conjunction with site- and time-specific weather information and records of all field operations.

Why Create GPS-Based Field Records?

GPS-based records for a farm field are the foundation for site-specific management in that field. First, they enable a grower to be proactive in his/her management of field scale variability. This includes the development of knowledge-based management zones and prescription maps for the variable application of different crop inputs such as fertilizer, seed, pesticides, lime and water (Doerge, 1998). Growers can also use GPS-based field records to add value to their grain. This is done by using these records to develop identity-preserved marketing plans which document the quality and history of a grain crop. These plans verify such things as crop hybrid or variety, planting history, field isolation, and the location of on-farm grain storage facilities.

Having complete GPS-based field records can also prepare growers to be more reactive to unexpected weather condi-tions or marketing opportunities. One on-farm example is the use of as-planted or as-sprayed maps broken out by date to explain the season-long impact of a sudden deterioration in weather and field conditions during planting or spraying. GPS-based records can also illustrate the consequences of intentional and unintentional cultural practices. For example, maps of field operations such as spraying, fertilization or tillage can be used to document the impact of any errors (skips or overlaps) made during these operations.

GPS-based field records can also have unanticipated off-farm benefits. The value or marketability of a grower's grain supply could be suddenly jeopardized if there is uncertainty about the presence of certain undesirable grain traits. Careful documentation ahead of time of seed type, crop location, field isolation and on-farm grain storage facilities could provide the assurance grain handlers might unexpectedly require if the grower has to document the quality of his product.

Use a GIS to Create New Spatial Information

Collecting time- and geo-referenced information is more than just a new (and better) way to collect, organize, view, and archive field information. Specialized software known as a Geographic Information System (GIS) can create new spatial information that is useful in managing farming operations more efficiently (ESRI Staff, 2001). Here are several possible examples.

  • Use field boundary maps to verify exact field acreage for calculating crop input requirements, developing crop insurance contracts and negotiating fair rental and lease agreements.
  • Spatially combine multi-year yield data and drainage tile line patterns from a field to evaluate the effect of tile proximity on crop yield . This analysis could then be used to predict locations within the field where additional tile lines may be profitable.
  • Use as-applied fertilizer, sprayer or tillage maps to evaluate the driving accuracy of tractor operators. Pass maps could be used to document the amount of overlaps and skips achieved by different operators.
  • Use the time, vehicle speed and swath width records from any field operation to develop equipment productivity reports . Results could be evaluated by operator, field, crop type, soil type, time of day, or any other factor included in the GPS-based field records.
  • Use GIS analysis of normalized yield maps from multiple crops to identify consistently high- or low-yielding areas that should be managed differently.
  • Analyze the value of crop protection practices . For example, in a corn field infested with common rust leave geo-referenced control (untreated) strips when spraying fungicides. Then at harvest, compare the yields of adjacent treated and untreated strips on the yield map.

Obviously, there are an almost unlimited number of ways that GPS-based field records could be used to better understand one's farming operation. Of course, this understanding must lead to improved decision making in order to add value to the overall operation.

Figure 1. Examples of typical time- and geo-referenced field records from a single field in Central Iowa. Click on each image for a larger map.

Field Boundary Map (JPG 8 KB)

NCRS Soil Survey Map (JPG 12 KB) Drainage Tile Map (JPG 11 KB) Topography Map (JPG 12 KB)

Field Boundary Map (JPG 8 KB)

NCRS Soil Survey Map (JPG 12 KB) Drainage Tile Map (JPG 11 KB)  Topography Map (JPG 12 KB)
Soil Electrical Conductivity Map (JPG 19 KB) TIGER® Data Map (JPG 14 KB) Bare Soil Photo (uncorrected) (JPG 12 KB) Bare Soil Photo (geo-referenced) (JPG 13 KB)
Soil Electrical
Conductivity Map
(JPG 19 KB)
TIGER® Data Map (JPG 14 KB) Bare Soil Photo
(JPG 12 KB)
Bare Soil Photo
(JPG 13 KB)
Plant Population Map (JPG 19 KB) As-Planted Map (JPG 16 KB) As-Applied Map (JPG 24 KB) Yield Map (JPG 16 KB)
Plant Population Map (JPG 19 KB) As-Planted Map (JPG 16 KB) As-Applied Map (JPG 24 KB) Yield Map (JPG 16 KB)

The most beneficial uses of these data will be farm and operator specific and will also depend on the level of GIS analytical support available. Creativity in the use of these analysis tools is the key to unlocking value for the precision farmer. Even if growers do not plan to utilize these records immediately, they are encouraged to collect them today. Many new precision farming tools will soon be available, but they will require these baseline data to realize their full benefits.

Bright Future for GPS-Based Record Keeping

In the future, expanded GPS-based field record keeping will greatly improve agronomic as well as enterprise management. At the farm level, machinery will be outfitted with new sensors that will allow managers to remotely monitor many aspects of vehicle and operator performance, including such things as fuel efficiency, engine temperature, fluid levels and driver productivity. Wireless communications between farm vehicles and a central office or a mobile Internet terminal will change the way farms are managed and quite probably the number of acres that a single operator can handle. New data-gathering tools will allow enterprise managers to determine where machinery is operating, how it is performing, when it needs to be serviced, how the crop is yielding, and what logistical decisions need to be made. These improvements depend on "seamless" data transfer that will occur as industry-wide data standards are implemented, making information more manageable and transportable. As this information becomes more accessible, managers can increasingly make data-driven decisions based on risk and objective economic considerations.

Enhancements in the software and hardware needed for identity-preserved grain production and marketing are also currently in development. New systems will soon be available that can develop geo-referenced planting plans, verify crop planting location and identification, confirm crop isolation requirements, monitor grain quality during harvest, and track grain movement through the marketing system.

Although innovations in technology will make data collection easier, the farm manager will still be responsible for the interpretation and validation of the data being collected. In the meantime, the ag software industry is making great strides in developing products that are increasingly powerful and easy to use. One type of software tool that is now in development is the Decision Support System (DSS) that predicts cropping outcomes based on crop growth simulation, detailed site characteristics and real-time and historical weather records. Growers who can use these new tools to mine their "spatial inventory" of GPS-based field records will be the ones who profit the most from their precision farming investment, both now and into the future.


Anderson, B. 1999. Maps as pre-season planning tools. Pioneer Hi-Bred Int'l Inc. Precision Update Issue 1. Pp. 1-2.

Doerge, T.A. 1998. Defining management zones for precision farming. Pioneer Hi-Bred Int'l Inc. Crop Insights Vol. 8 No. 21. Pp. 1-6.

ESRI Staff. 2001. Environmental Systems Research Institute, Inc.

Peterson, T.A. and T.A. Doerge 1998. Using GPS for mapping site features and field operations. Pioneer Hi-Bred Int'l Inc. Precision Update. Issue 2. Pp. 1-2.

* Topologically Integrated Geographic Encoding and Referencing system

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