About the Map Viewer - Frequently Asked Questions
What is the Calflora Map Viewer?
The Calflora Map Viewer is a web application for visualizing
where wild plants have been observed, by showing
colored points against a relief map of California.
By clicking on a point, you can see the corresponding
The viewer will zoom to fifteen different levels.
To make the location
of observation points more comprehensible,
the viewer offers various optional features
including roads (two levels) and a grid.
The viewer can show labels on the map; for instance,
the names of towns, mountains, streams, etc.
The viewer can also show shaded polygonal areas,
such as those indicating watersheds (from Calwater 2.2, at five levels),
or GAP plant community regions.
Sometimes a set of observations is linked to
a polygonal area (such as when a botanist made a list
of all plants within the boundaries of a particular state park).
When this is the case,
the viewer can show these observations either as
a shaded polygon or as points.
How do I start the viewer?
Click the button, and the viewer will come up showing
all of Santa Barbara County, and points indicating
where the plant has been observed.
To start the viewer, enter a query to the Calflora
For instance, look for
in Santa Barbara County.
If there are any georeferenced points that match your
criteria, the results page will show a small map
of the county and a link to the
map viewer that looks like this:
How do I use the viewer?
Use the control on the left side of the screen to zoom in or out.
Use the small beige map in the upper right to
re-center the map. (Note that you can use this control
to move anywhere in the state).
If it is too difficult to see the points or the names,
use the Relief Intensity control to soften the relief layer.
You can also turn the relief map completely off (best for printing).
The color of the points indicates documentation type --
for instance, blue points indicate specimen data.
Mouse over a point to see the location description and
species observed. Click on a point to see full details of the
Where does the map data come from?
The Calflora Map Viewer has two basic parts:
a map server, and a user interface.
The server generates images from
1. raster data (image files showing relief features), and
2. vector data (points, lines, and polygons).
The server uses a library of raster data for the relief layer,
consisting of JPEG image files generated by GlobalMapper
from USGS NED and DEM files.
The server uses a library of vector data to generate
a foreground image (superimposed over the relief layer
by a web browser).
The foreground image contains observation points and any user-selected features
(roads, streams, various polygons, names, etc.).
Source data for the vector library comes from
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
Geographic Names Information System.
Polygons for East Bay regions
were prepared by Heath Bartosh for the
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
Polygons for Bay Area Open Space areas are from
Other polygons were contributed by the
Sonoma County Agricultural Preservation and Open Space District
Monterey Peninsula Regional Park District
(John Schweisinger, Turf Image),
Land Trust of Napa County
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).
In a case like this, the unshown points are very close
to the shown points. They are so close that even at the maximum zoom
level, you would not see them as distinct.
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
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
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
If you want to bookmark a particular map,
there is a link labeled
on the bottom right.
If you click on the link, the browser will show
the same map, but the URL will be bookmarkable.
If you want to email the page to somebody,
you can right click over the link and select
Copy Link Location or Copy Shortcut,
and then paste the URL into an email.
GAP Plant Communities
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
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 amount of land that is primarily urban or agricultural, and
the complexity of the California landscape, and
how much work it would take to map it more fully.
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
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
between the Holland communities and
A Manual of California Vegetation,
Sawyer and Keeler-Wolf 1995.
General Information Regarding Holland Communities.)
What kind of information can the Map Viewer show?
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
GAP polygons showing 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.
if you have further questions,
or suggestions for features you'd like to see or to contribute.