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Internal NoData in Alaska zones: Be aware that there is internal NoData within the Alaska layers due to a lack of primary input data. The instances of NoData are relatively small and are generally on the Canadian border and on islands. LANDFIRE NoData is coded -9999.

Background:

A primary quality control for LANDFIRE data products is to ensure that there is no internal NoData. This data standard was held for all zones in the lower 48. However, due to lack of satellite imagery in some instances and elevation data in others, there is internal NoData in data products within some zones in Alaska. The regions of NoData are relatively small and generally fall along the border of Canada as well as some far eastern-reaching islands.

The instances of NoData are not always coincident between data products. For example, elevation data and the elevation-derived slope and aspect are missing for the northern and southern portions of Prince Edward Island, while satellite imagery is available for these areas. Along the Canadian border, subtle inconsistencies between the available satellite imagery and elevation data result in possible NoData conflicts, not only between the imagery and terrain data but also with modeled data products, such as existing vegetation and fuel layers.

Advice:

Be aware that there is internal NoData in the Alaska LANDFIRE layers. The designated NoData value for LANDFIRE is -9999. FARSITE and FLAMMAP treat the -9999 value as NoData. However, understand that any GIS analysis will treat -9999 as a real value, and it remains the user’s responsibility to recode the -9999 to null if necessary.

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