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Home GRS News New Resource Sampling Study - "You CAN have your cake and eat it Too!"


UN-FAO Resource Sampling Study Recommends Use of Line-point Transect and GRS Densitometer

October 30, 2015 - For Immediate Release

"The line-point transect forest cover assessment method was the most accurate,least expensive, and most easily applied among the four methods tested. This method is scientifically accurate and records forest canopy and floor cover as a set."

This is the major conclusion of a recent study undertaken by the Food and Agriculture Organization of the United Nations (FAO) when they recently presented the results of their study "Testing Field Methods for Assessing the Forest Protective Function for Soil and Water" this past September at the XVI World Forestry Congress held in Durban, South Africa.  In conjunction with this study the FAO has also published a second paper "Field Guide for Rapid Assessment of Forest Protective Function for Soil and Water" that describes their recommended use of the line- point transect and GRS Densitometer to assess forest ecosystems.

The FAO study, conducted by three partner organizations in Mexico, Nepal, and Viet Nam evaluated four different methods of assessing canopy cover characteristics of both the overstory and understory.  After extensive testing and evaluation by different researchers in these three countries to determine the best approach, the study also mentioned that the sampling instrument used in this recommended approach was the GRS Densitometer.  The FAO study recommends this approach to forest inventory practitioners and researchers to enhance data collection and reporting for such assessments, as it will help to improve capacity that support national inventories and
Global Forest Resources Assessments.  

The finding that the line-point methodology is the "most accurate, least expensive, and most easily applied" approach seems to violate the basic premises of the Time-Cost-Quality triangle in which one can normally achieve two of these project characteristics while having to sacrifice or compromise the third.   This combination of sampling characteristics is what makes this approach so valuable, as often the most accurate means of collecting field data is also the most expensive method.

Ken Stumpf of Geographic Resource Solutions (GRS), who has been implementing this methodology during GRS's inventory and mapping projects since the early 1990's says "we have found this approach to be very easy to teach our staff and implement in the field. We have even been able to present workshops to high school students and then hire some of these students to work alongside our professional foresters and botanists as they perform ecological assessments at field sites.  It is extremely beneficial to our inventory and mapping efforts that we can develop very detailed, accurate, and standardized results, regardless of the level of expertise of the field staff. This leads to an overall reduction in the costs of collecting field information while still collecting high quality information."  This is potentially a major benefit to organizations that may rely on temporary seasonal staff or volunteers to perform such field data collection and assessment activities.

GRS actually uses this approach to sample and describe all types of ecosystems that also represent herbaceousand shrub lifeforms. Their adaptations to this sampling methodology enable the development of species-specific cover estimates by canopy layer, as well as estimates by tree size class. Other adaptations have enabled the development of species-specific estimates of average tree diameter, height, and stems per acre. Other sampling protocols, such as the Brown's Transect, have been easily integrated into the line-point sampling approach that have enabled the development of coarse and fine woody debris estimates necessary to develop fire fuel models, as well as species-specific estimates of tree volume and biomass.  Such accurate and standardized field descriptions have supported GRS in their collection of ground truth and accuracy assessment information as they have mapped millions of acres of wildlands, including four National Parks, in California, Alaska, and the Pacific Northwest since 1989.

GRS currently supports the use of the GRS Densitometer through their Education Program that includes teachers and students from middle school introductory science and biology programs to graduate school PhD students.  During just the past 5 years GRS has supported over 90 universities, high schools, and middle schools in their use of this sampling methodology in their academic programs.

To access these FAO reports simply use the following links:

FAO Documents:

"Testing Field Methods for Assessing the Forest Protective Function for Soil and Water" can be accessed at

"Field Guide for Rapid Assessment of Forest Protective Function for Soil and Water" can be accessed at

For more information regarding GRS and the GRS Densitometer visit their website at or
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About Geographic Resource Solutions:

GRS, located in Arcata CA, was founded in 1989 to provide natural resource information development and consulting services.  Such services include natural resource inventory, mapping, analysis, and modeling.  GRS is known for their Discrete Classification Mapping Methodology, an approach that enables the mapping of species-specific cover as a continuous value, as well as for the GRS Densitometer, a cover sampling field inventory tool. Since 1989 GRS has inventoried and mapped over 50-million acres of wildlands in California, Alaska, and the Pacific Northwest.

For more information contact

Ken Stumpf
Director, Resource Management Applications
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GSA# GS-10F-0451NESRI Consultant