Photo interpretation

Vegetation Resources Inventory (VRI)

The Vegetation Resources Inventory (VRI) is carried out in two phases:

1. The Photo Interpretation phase (Phase 1) involves estimating vegetation polygon characteristics from aerial photographs
2. The Ground Sampling phase (Phase 2) provides the information necessary to determine how much of a given attribute is within the inventory area and to verify the accuracy of the photo estimates

VRI photo interpretation is carried out based on principles of the photo interpretation process, a rigorous Quality Assurance process, and in accordance with published VRI standards and procedures. The provincial land cover is delineated into polygons based on similar characteristics and assigned attributes based on a combination of mid-scale aerial photography, ground and air calibration and other data sources. VRI photo interpretation provides wall-to-wall coverage of the entire provincial land base regardless of vegetation values or ownership. 

Principles of VRI photo interpretation:

• The VRI will cover the entire land base of British Columbia, irrespective of ownership or vegetation values
• The vegetated land base will be delineated into polygons based on similar vegetation characteristics visible on mid-scale aerial photography
• Areas of non-vegetated lands will be delineated into similar polygons, and basic attributes will be assigned at the level achievable by photo interpreters with minimal additional training. Such polygons may be further described by experts in a separate process if desired
• Vegetated and non-vegetated attributes that are not visible on the project aerial photography at the attribution scale given for the project, due to the overtopping vegetation and shadows of the surrounding vegetation, are not to be incorporated into the description of the delineated polygon. Any deviation from this photo interpretation principle must be endorsed in the inventory project plan
• The inventory design does not allow polygon boundaries to be changed by the sampling process
• The estimate for a polygon will describe land cover types according to the British Columbia Land Cover Classification Scheme
• The estimation of polygon attributes may indicate that several cover types exist within a polygon boundary. Several land cover types may be described as additional information for resource users
• All continuous variables will be estimated to the finest level of resolution practical; class-based summaries can be compiled as desired from the detailed data
• Ancillary data will be used, as available, to provide accurate and consistent estimates of polygon attributes

The photo interpretation process strives towards consistency of estimates:

• By one classifier
• Between classifiers
• Over time