Source data for the vector library comes from many places. Roads, lakes, and the coastline are from US Census Bureau Tiger/Line files. Streams are from the USGS National Hydrology Dataset. The names and positions of towns, mountains, etc. are from the USGS Geographic Names Information System.

Polygons for East Bay regions were prepared by Heath Bartosh for the East Bay CNPS Rare and Unusual Plants Program (EBRUP) and generously contributed.

Polygons for many parks and reserves are from the California Spatial Information Library, Public, Conservation and Trust Lands (PCTL) dataset. Other polygons were generously contributed by the Sonoma County Agricultural Preservation and Open Space District (Tom Robinson), Monterey Peninsula Regional Park District (John Schweisinger, Turf Image), and the Land Trust of Napa County (John Hoffnagle; Megan Torres, Green Info Network).

Point locations come from the Calflora observation database, in decimal latitude/longitude format, NAD83 datum.

Why doesn't it show the other points?
On the result page for an observation query, you may see a message like the following:

The map shows 3 out of 5 available georeferenced point(s).

I asked to see observations of a particular species in county X, and the map shows points in county Y.
This is data problem. The point georeferenced within county Y is labeled as being in county X, so it appears when you ask to see things in county X. Either the georeference information is incorrect or the county label is incorrect. You can contact the data contributor and point out the discrepancy.

Also, as you look at the points, bear in mind that each point has a location precision. For some points it may be a few feet; for others as much as a mile. For such imprecise points, the plant was observed somewhere near where it it shown, but probably not exactly where it is shown.

Data contributors: if you think Calflora is incorrectly displaying some of your data, please contact us and we will try to fix the problem.

Can I bookmark a map viewer page, or send the URL to a friend so that they can see exactly the same map?
When the map viewer is first invoked from the Calflora plant observation query results page, it uses the post method to accomodate potentially voluminous point data. Notice that in the browser URL field, the URL has no no parameters such as zoom level or center point. If you were to bookmark the page, the position and size of the map you are seeing are not included in the bookmark, so when you return to the bookmark, you end up in the viewer's default location (western Nevada).

If you want to bookmark a particular map, there is a link labeled

Link to this page

What are GAP Plant Communities ?
The California Gap Analysis Project was completed in 1998 and published by the Biogeography Lab, University of California, Santa Barbara. Data from the project includes over 27,000 polygons covering the state, where each polygon is identified as to plant community (according to the Holland system) and wildlife habitat type (according to the California Wildlife Habitat Relationships system). The purpose of the project was to find plant communities or species (plant and animal) potentially at risk because they occur primarily on private land. (As an example of how the data has been used, see Biodiversity in the Southwestern California Region, David M. Stoms and Frank Davis.)

The GAP polygons are included in the Calflora Map Viewer as an optional background to provide a sense of local context for the plant observation points. For instance, if you see that a plant observation occurs in an area identified as Alluvial Redwood Forest by the GAP data, that may give you a rough idea of the immediate environment in which the plant was growing.

There are many things to bear in mind when looking at the GAP data. As prepared by the GAP project, each polygon has a primary plant community. Some also have secondary and tertiary plant communities. The map viewer shows only the primary community. For any polygon, the primary community is understood to be the most important community in the whole area of the polygon. There may be areas of other plant communities within a polygon, which are not represented in the data or on the map. For example, the entire County of San Francisco shows on the map as Urban or Built-up Land, but in fact there are relatively small areas of costal scrub and various dune communities present there. For another example, on the coast of Mendocino County, what shows on the map as large areas of Bishop Pine Forest actually has smaller ares of coastal scrub and coastal prairie within it. In general, plant communties occurring in small areas (e.g. riparian corridors) are under-represented in the data. If you know a natural area well, you will probably find its representation in the GAP polygons to be overly simple.

In spite of any limitations, the GAP data can supply a useful level of background information, and there is no other dataset that matches it for completeness or detail. Visual presentation of the data dramatizes

The basic technique of the GAP project (analysis of aerial photos plus site visits) has since been improved upon; see particularly the Napa Vegetation Mapping Project (James Thorne et. al.).

Finally, is the juxtaposition of Calflora plant observation data with GAP plant community polygons predictive? For example, if you see a point occurrance of some species coinciding with a polygon representing a redwood forest, does it mean that that species grows in redwood forests? The simple answer is no, because the data is not detailed enough. But, used in conjunction with other sources of information (e.g. the location description of the observation, or the coincidence of many points of the same species with a single plant community), this data may help to strengthen or weaken such a prediction.

Map View User Interface. When you first turn on GAP Plant Communities, the viewer selects all GAP polygons that overlap the currently selected map area. The viewer groups these polygons by community, sums the cumulative area of each community, and sorts the communities by area. The list of communities represented in the current map appears at the bottom of the page. By default, the viewer selects the three largest communities, and shows the polygons associated with these communities shaded in various colors on the map. You may select any communities you would like to see shaded, and press Redisplay.

By default, similar communities are displayed in the same color (there are 200 communities and 30 colors). For instance, all coastal scrub communities are displayed in the same color. If more than one coastal scrub community is represented in the current map area, and you would like to see each shaded with a different color, then select the Use a different color for each community option at the bottom of the page.

The Holland system of plant communities was in use by the Califormia Natural Diversity Data Base in the 90's, but was never published and has since fallen out of use. Thus, as of this writing, there is no place on the web where these communities are fully described. The closest is a translation table between the Holland communities and series from A Manual of California Vegetation, Sawyer and Keeler-Wolf 1995. (See also General Information Regarding Holland Communities.)

What kind of information can the Map Viewer show?
Examples:

	Observations of Blue oak, Quercus douglasii, in Shasta and Tehama Counties with GAP polygons showing Blue Oak Woodland
	Observations from UC Riverside Herbarium in western Riverside County above 2000 meters (all species)
	GAP polygons showing Urban areas and Redwood forests in the greater Bay Area
	Observations of yellow star thistle, Centaurea solstitialis, in Tulare County with GAP polygons showing agricultural land
	Observations of Arctostaphylos species around the Bay Area, including regions from the East Bay CNPS Rare and Unusual Plants database, quads from the CNPS Inventory Database, and points from other sources.
	Observations of Arctostaphylos species from Santa Barbara and San Luis Obispo Counties, including quads from the CNPS Inventory Database and points from other sources.
	Observations from the Marin CNPS chapter.
	Observations from the Monterey CNPS chapter, with watersheds at the Calwater 'Hydrologic Area' level.

Contact us if you have further questions, or suggestions for features you'd like to see or to contribute.