The following is an excerpt from a paper submitted by RECON Enviromental, Inc. Titled "Land Cover Data Assessment in Pima County" The GAP Analysis Program (GAP) is a national effort to map habitats in every state for use in assessing the status of long-term maintenance of biodiversity (Scott et al. 1993). The Arizona GAP program began in 1991 and was housed within the Advanced Resources Technology Program (ART) in the School of Renewable Natural Resources at the University of Arizona. The initial program, including land cover mapping for Arizona, was directed by Dr. Lee Graham from 1991 to 1995 (Kunzmann et al. 1998). The Arizona GAP vegetation coverage, 1993, was mapped using remote sensing techniques. Landsat Thematic Mapper (TM) satellite imagery (30 meter resolution scenes from 1991) was digitally classified to differentiate potential vegetation communities. One hundred five classes were aggregated from the imagery based on similarities in their spectral signatures. Vegetation types associated with these classes were assessed and assigned by reviewing airborne video imagery of the same areas. Video transects, flown in fall 1991 and summer 1992 and covering one-third to one-half mile swaths, were reviewed together with field data and historic vegetation data to help interpret vegetation classes (U.S. Fish and Wildlife Service 2000). The original Arizona GAP vegetation classification system developed by Graham was roughly modeled on Brown, Lowe, and Pase (1979) but classification units are not hierarchical. Graham's descriptive vegetation community names correspond to both series and association level BLP classes and reflect the ecotonal nature of vegetation mapped at this scale for Pima County (Kunzmann, pers. com. 2000) In 1996, the U.S. Geological Survey (USGS) Cooperative Park Studies Unit (CPSU) received funding from the National GAP Program to assess the GAP mapping effort and convert the Graham land-cover types to a standardized classification system (Kunzmann et al. 1998). More than eight percent of the 58,000 originally mapped land cover polygons were sampled and classified. Original polygon boundaries were not modified but the original descriptive names were cross-walked into a BLP series level classification, reducing the number of vegetation types from 105 to 53 for Arizona (from 45 to 22 for Pima County). Scoring agreement between the Graham map polygons and the CPSU field classifications, it was found that the Graham map was 82 percent accurate at the biome level and 68 percent accurate at the series level for all vegetation classes. Agricultural and urban lands scored highest for estimated thematic accuracy (88 percent and 85 percent, respectively), followed by forest/woodland (75 percent), desertscrub (74 percent) and grassland (72 percent). Scrubland types were found to be fairly accurately classified (64 percent) and riparian forests the least well-classified (57 percent) (Kunzmann et al. 1998). Metadata for this GIS data is available at the University of Arizona GAP website (http://www.srnr.arizona.edu/nbs/gap/gapvegdoc.html), although there is little detail about mapping methods or coverage attributes. From our investigation of this data we learned that the attribute "hab-type" in the GIS coverage holds the Lee Graham descriptive type name. The "biome_series" attribute contains the CPSU BLP series name. And the jbk# attribute contains the corresponding JBK code for the BLP name. The main advantage of this dataset is that it covers all of Pima County and it has a uniform level of classification (BLP series) throughout GAP mapping does not adequately delineate the long, slender polygons that comprise riparian vegetation, but it does include larger areas of sacaton grassland and marsh, which are important habitat types. Based on the CPSU assessment, GAP vegetation mapping provides a good course-scale classification of land cover, especially given the inherently complex and ecotonal nature of Arizona vegetation (Kunzmann et al. 1998). And for the purposes of the SDCP, GAP provides an essential data layer on which to build an improved composite land cover map. GAP mapping used in the composite land cover map is shown in Figure 1. Colors differentiate series level CPSU data. Additional polygon boundaries based on Graham's vegetation description are also retained in this coverage. CPSU researchers recommend that these additional boundaries should be used only to show heterogeneity in series level polygons, but should not be used to delineate additional types (Kunzmann, pers com. 2000). ************************************************************************** The following is metadata taken from the website: (http://www.srnr.arizona.edu/nbs/gap/gapvegdoc.html) GAP AZ Vegetation coverage NAME OF DATA SET: AZHEC40Y DATA TYPE: Vector; Polygon DESCRIPTION OF CONTENT: Arizona Actual Vegetation, 1993 mapped at a resolution of 40 hectares. Developed by the National Biological Survey's Arizona GAP Analysis Program for use in assessment of the status of long-term maintenance of biodiversity in Arizona. FORMAT: Arc/Info DATA SIZE (Approximate Megabytes): Data Set 7.5" Quad 109 N.A. HISTORY: Landsat Thematic Mapper imagery (scene dates mostly 1991, with some 90 and 92) was digitally classified using a hybrid unsupervised and unsupervised classification methodology. First, 3 input bands (NDVI, a 5/4 band ratio indicating moisture content of vegetation, and a local texture band built from the NDVI) were used in a unsupervised maximum likelihood classification procedure. The result of the unsupervised classification procedure, in which buffered GPS-referenced airborne video sample points indicating vegetation association were used as training sets. The resulting image was then edited manually to correct classification errors, then converted to ARC/Info vector format. Vegetation descriptions are based on a modified Brown, Lowe, and Pase classification system, and will be cross-walked to a UNESCO coding scheme for National GAP Program purposes. Satellite image dates are mostly 1991, with some 90 and 92 scenes. Airbome video imagery (1/3 to 1/2 mile horizontal swath width in wide angle, with interval zooms to 12X occurring approximately every 9 seconds, or 1500 m) was flown in the Fall 1991 and Summer 1992. Most video transacts were spaced approximately 30 km apart, in an E-W trajectory. MAINTENANCE: NONE ** There are some know errors in this data set. ** PROJECTION: UTM Zone 12 Meters ACCURACY EXPLANATION: Accuracy of the map is currently being assessed. DISTRIBUTION LIABILITY: The National Biological Survey assumes no responsibility for application of the data beyond their original intent. DATA SET CITATION: Graham, L.A. 1995. Arizona natural vegetation, as mapped for the Arizona GAP Analysis Program. Digital GIS File. School of Renewable Natural Resources, University of Arizona, Tucson, AZ. USE RESTRICTIONS: Copyright 1995. This information is not accurate for legal boundary, or for navigation purposes. This information is intended for use by the National Biological Survey's Gap Analysis Program. Any other uses of these data are not the responsibility of the author or the State or the National Gap Analysis Program. ITEMS: Item name: AREA Description: The value of each polygon in square meters. Format: 4,12,F,3 Item name: PERIMETER Description: Perimeter of the polygon arcs in meters. Format: 4,12,F,3 Item name: AZHEC40Y# Description: This is a unique internally assigned identification number for each polygon. Format: 4,5,B Item name: AZHEC4OY-ID Description: User assigned identification number for each polygon Format: 4,5,B Item name: GRID-CODE Description: Unknown Format: 4,8,B Item name: VC Description: Numerical vegetation code Format: 3,4,N,0 Item name: VTYPE Description: Vegetation description Format: 50,51,C Code Table: Acceptable values for VC and VTYPE are below. 3 "Englemann Spruce-Mixed Conifer" 4 "Rocky Mt. Lichen-Moss" 5 "Rocky Mt. Bristlecone-Limber Pine" 6 "PJ-Shrub/Ponderosa Pine-Gambel Oak-Juniper" 7 "PJ/Sagebrush/Mixed Grass-Scrub" 8 "Pinyon-Juniper-Shrub Live Oak-Mixed Shrub" 9 "PJ (Mixed)/Mixed Chapparal-Scrub" 10 "Pinyon-Juniper-Mixed Shrub" 11 "Pinyon-Juniper-Mixed Grass-Scrub" 12 "Pinyon-Juniper (Mixed)" 13 "Douglas Fir-Mixed Conifer" 14 "Arizona Cypress" 15 "Ponderosa Pine" 16 "Ponderosa Pine-Mixed Conifer" 17 "Ponderosa Pine-Gambel Oak-Juniper/Pinyon-Juniper" 18 "Ponderosa Pine/Pinyon-Juniper" 19 "Ponderosa Pine-Aspen" 20 "Ponderosa Pine-Mixed Oak-Juniper" 21 "Encinal Mixed Oak" 22 "Encinal Mixed Oak-Pinyon-Juniper" 23 "Encinal Mixed Oak-Mexican Pine-Juniper" 24 "Encinal Mixed Oak-Mexican Mixed Pine" 25 "Encinal Mixed Oak-Mesquite" 26 "Encinal Mixed Oak/Mixed Chapparal/Semidesert Grass" 27 "GB Juniper" 28 "Int. Chapparal-Shrub Live Oak-Pointleaf Manzanita" 29 "Int. Chaparral-Mixed Evergreen Sclerophyll" 30 "Int. Chaparral (Mixed)/Son. Paloverde-Mixed Cacti" 31 "Int. Chapparal (Mixed)/Mixed Grass-Scrub Complex" 32 "Rocky Mt/GB Dry Meadow" 33 "Madrean Dry Meadow" 34 "GB Mixed Grass" 35 "GB Mixed Grass-Mixed Scrub" 36 "GB Mixed Grass-Sagebrush" 37 "GB Mixed Grass-Saltbush" 38 "GB Mixed Grass-Mormon Tea" 39 "Semidesert Tobosa Grass-Scrub" 40 "Semidesert Mixed Grass-Yucca-Agave" 41 "Semidesert Mixed Grass-Mesquite" 42 "Semidesert Mixed Grass-Mixed Scrub" 43 "GB Sagebrush" 44 "GB Big Sagebrush-Juniper-Pinyon" 45 "GB Sagebrush-Mixed Grass-Mixed Scrub" 46 "GB Shadscale-Mixed Grass-Mixed Scrub" 47 "GB Greasewood Scrub" 48 "GB Saltbush Scrub" 49 "GB Blackbrush-Mixed Scrub" 50 "GB Mormon Tea-Mixed Scrub" 51 "GB Winterfat-Mixed Scrub" 52 "GB Mixed Scrub" 53 "GB Mormon Tea/Pinyon-Juniper" 54 "Mohave Creosotebush Scrub" 55 "Mohave Creosotebush-Bursage-Mixed Scrub" 56 "Mohave Creosotebush-Yucca spp. (incl. Joshuatree)" 57 "Mohave Blackbrush-Mixed Scrub" 58 "Mohave Blackbrush-Yucca spp. (incl. Joshuatree)" 59 "Mohave Saltbush-Mixed Scrub" 60 "Mohave Brittlebush-Creosotebush Scrub" 61 "Mohave Creosotebush-Brittlebush/Mohave Globemallow" 62 "Mohave Catclaw Acacia-Mixed Scrub" 63 "Mohave Joshuatree" 64 "Mohave Mixed Scrub" 65 "Chihuahuan Creosotebush-Tarbush Scrub" 66 "Chihuahuan Mesquite Shrub Hummock" 67 "Chihuahuan Whitethorn Scrub" 68 "Chihuahuan Mixed Scrub" 69 "Sonoran Creosotebush Scrub" 70 "Sonoran Creosotebush-Bursage Scrub" 71 "Sonoran Creosotebush-Mesquite Scrub" 72 "Sonoran Creosotebush-Bursage-Paloverde-Mixed Cacti" 73 "Sonoran Brittlebush-Mixed Scrub" 74 "Sonoran Saltbush-Creosote Bursage Scrub" 75 "Sonoran Paloverde-Mixed Cacti-Mixed Scrub" 76 "Sonoran Paloverde Mixed Cacti/Sonoran Creosote-Bur" 77 "Sonoran Paloverde-Mixed Cacti/Semidesert Grassland" 78 "Sonoran Crucifixion Thorn" 79 "Sonoran Smoketree" 80 "Sonoran Catclaw Acacia" 81 "Madrean Riparian/ Wet Meadow" 82 "Agriculture" 83 "Urban" 84 "Industrial" 85 "Mixed" 86 "Playa/Semi-Permanent Water" 87 "Water" 90 "GB Riparian/Cottonwood-Willow Forest" 91 "GB Riparian Forest/Mixed Riparian Scrub" 92 "GB Riparian/Sacaton Grass Scrub" 93 "GB Riparian/Reed-Cattail Marsh" 94 "GB Riparian/Wet Mountain Meadow" 95 "Int. Riparian/Cottonwood-Willow Forest" 96 "Int. Riparian/Mixed Broadleaf Forest" 97 "Int. Riparian/Mesquite Forest" 98 "Int. Riparian/Mixed Riparian Scrub" 99 "Son. Riparian/Cottonwood-Willow Forest" 100 "Son. Riparian/Cottonwood-Mesquite Forest" 101 "Son. Riparian/Mixed Broadleaf Forest" 102 "Son. Riparian/Mesquite Forest" 103 "Son. Riparian/Leguminous Short-Tree Forest/Scrub" 104 "Son. Riparian/Mixed Riparian Scrub" 105 "Son. Riparian/Sacaton Grass Scrub" 106 "Son. Riparian/Low-lying Riparian Scrub" 107 "Son./Chih. Riparian/Reed-Cattail Marsh" 108 "Riparian/Flood-damaged 1993" 109 "State Boundary" Item Name: HECTARES Description: The value of each polygon in hectares. Format: 16,16,I