California Farms

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The California State Department of Conservation Farmland Mapping and Monitoring Program (FMMP) ( has farm data for the state that can be used in OSM. FMMP Manager Molly Penberth confirmed the data are available under a public domain license as long as attribution is given as described on their site.


The 2010 data are being added as they are released. This started in spring of 2011 and uploads continue as new data are released. The data are previewed first, sometimes with multiple OSM contributors collaborating. The data can be shared in .xml or .osm format, then people who are familiar with the areas can download them, clean them up in JOSM using imagery to align objects and make the tags sound and correct and then upload. Contributors should compare the FMMP data with the existing data, replacing old farm data with new farm data when possible.

OSM should use this data set for importing just the farmland. Urban lands should not be used because they are too broad: it is not always clear whether an entire "urban land" zone is purely residential, commercial or industrial, for example (often it is not). The water layer should also be avoided because the NHD import has more accurate data.

These data are included in the California Land Cover data sets, but these FMMP data are more accurate and should be done first before that import is attempted.



The data are updated every two years. FMMP is looking for a way to be able to update the data when they are changed and also to see what changes have been made. They would also like to be able to contribute back to OSM and in turn be able to reference the data from OSM when it changes. There currently aren't any good methods to sync data like this (except in a painstaking manual way), but we should look for ways to help them and collaborate where possible.


FMMP data are slightly misaligned and appear to be off when viewed with aerial photos or OSM data. FMMP is saved in NAD27 and needs to be converted to WGS84. While the data are generally good, it's almost as if the whole layer needs to be shifted slightly to make it align. It could simply be a matter of the projection conversion. Maybe there is another way to automatically convert it. In JOSM, select all the items at once and then move them up slightly to allign with the imagery.

Crossing layers

Some layers may cut across a field that looks like it should all be one area. FMMP classifies farm data as prime farmland, farmland of statewide importance, farmland of local importance or unique farmland.

Lack of details

OSM is more detailed than FMMP data when it comes to farms. OSM supports vineyards, orchards and farmyards among some of the variations in farms. FMMP makes no distinction between what the land is used for, with the exception of grazing, which we are mapping to landuse=meadow. When possible and appropriate, please change landuse=farm to landuse=vineyard or landuse=orchard.

Existing data

Some counties such as Fresno, Kern and Santa Cruz and Napa already have farm data imported on the parcel level. If newer FMMP data are added here, they would have to be merged with data already extant in OSM. Be very cautious in attempts to do this (though it is welcome, especially for newer updates), as merging existing (old) data and new data is NOT one of OSM's strongest suits.


The data included some huge relations. These should be broken apart into smaller areas whenever possible, using natural breaks likes roads, tracks or rivers.

How the data are defined


  • Prime Farmland (P) - Farmland with the best combination of physical and chemical features able to sustain long term agricultural production. This land has the soil quality, growing season, and moisture supply needed to produce sustained high yields. Land must have been used for irrigated agricultural production at some time during the four years prior to the mapping date. Download information on the soils qualifying for Prime Farmland.
  • Farmland of Statewide Importance (S) - Farmland similar to Prime Farmland but with minor shortcomings, such as greater slopes or less ability to store soil moisture. Land must have been used for irrigated agricultural production at some time during the four years prior to the mapping date.
  • Unique Farmland (U) - Farmland of lesser quality soils used for the production of the state's leading agricultural crops. This land is usually irrigated, but may include nonirrigated orchards or vineyards as found in some climatic zones in California. Land must have been cropped at some time during the four years prior to the mapping date.
  • Farmland of Local Importance (L) - Land of importance to the local agricultural economy as determined by each county's board of supervisors and a local advisory committee.
  • Grazing Land (G) - Land on which the existing vegetation is suited to the grazing of livestock. This category was developed in cooperation with the California Cattlemen's Association, University of California Cooperative Extension, and other groups interested in the extent of grazing activities. Currently tagged as landuse=meadow.
  • Urban and Built-up Land (D) - Land occupied by structures with a building density of at least 1 unit to 1.5 acres, or approximately 6 structures to a 10-acre parcel. This land is used for residential, industrial, commercial, construction, institutional, public administration, railroad and other transportation yards, cemeteries, airports, golf courses, sanitary landfills, sewage treatment, water control structures, and other developed purposes.
  • Other Land (X) - Land not included in any other mapping category. Common examples include low density rural developments; brush, timber, wetland, and riparian areas not suitable for livestock grazing; confined livestock, poultry or aquaculture facilities; strip mines, borrow pits; and water bodies smaller than forty acres. Vacant and nonagricultural land surrounded on all sides by urban development and greater than 40 acres is mapped as Other Land.
    • The Rural Land Mapping Project provides more detail on the distribution of various land uses within the Other Land category in nine FMMP counties, including all eight San Joaquin Valley counties. The project may be expanded to the entire FMMP survey area as funding becomes available. The Rural Land categories include: Rural Residential Land (R), Semi-Agricultural and Rural Commercial Land (sAC), Vacant or Disturbed Land (V), Confined Animal Agriculture (Cl) -- status of this land use relative to Farmland of Local Importance or Nonagricultural or Natural Vegetation (nv).
    • It should go without saying, but we'll say it anyway: before uploading anything from this survey, first preview/view the data using JOSM. Helpful additional layers are aerial/satellite photography layers (such as Bing Sat) and the actual OpenStreetMap layer itself; toggle these using the "eye" icon. See if similar data have already been uploaded or manually added, and if so, choose the "best" (more recent, more accurate, "better") data.


- These rules can be used with the Java Shp-to-osm.jar script.

outer,polygon_ty,,attribution,Farmland Mapping and Monitoring Program
outer,polygon_ty,P,description,prime farmland
outer,polygon_ty,S,description,farmland of statewide importance
outer,polygon_ty,L,description,farmland of local importance
outer,polygon_ty,U,description,unique farmland
outer,polygon_ty,G,description,grazing land
outer,polygon_ty,X,description,other land 
# check to see if there is a better tag individual like farmyard

outer,county_nam,con,addr:county,Contra Costa
outer,county_nam,eld,addr:county,El Dorado
outer,county_nam,los,addr:county,Los Angeles
outer,county_nam,sbt,addr:county,San Benito
outer,county_nam,sbd,addr:county,San Bernardino
outer,county_nam,sdg,addr:county,San Diego
outer,county_nam,sjq,addr:county,San Joaquin
outer,county_nam,slo,addr:county,San Luis Obispo
outer,county_nam,smt,addr:county,San Mateo
outer,county_nam,sba,addr:county,Santa Barbara
outer,county_nam,scl,addr:county,Santa Clara
outer,county_nam,scr,addr:county,Santa Cruz
outer,county_nam,srv,addr:county,Sierra Valley


  • Download files from FMMP FTP site
  • Open them in Qgis and remove water and urban layers. Save as WG84.
  • Run script on shapefile to convert to .osm format.
  • Open file or files in JOSM and merge into one file. Remove duplicate nodes using Validator. Manually change other land areas to their correct tag using aerial images. Look for any areas that may need to be adjusted slightly.
  • Save the file. Check and see if there are one or more additional OSM contributors in the area who can help verify.
  • Open the file in JOSM once again and see if it contains either more than about 200 distinct polygons (including multipolygons), or is larger than 1 or 2 megabytes. If so, consider splitting it up into sub-files. A recommended (successful in Monterey County) method is to search for each type of landuse (farmyard, scrub, meadow, et cetera -- we find there to be about 15 to 20 different types) and create a sub-file containing all polygons of each landuse type.
  • Check the (large, single) file or each sub-file against at least 1) Visual imagery like the Bing layer in JOSM, 2) Existing OSM data (don't try to download the whole county, rather areas only immediately surrounding each polygon in the file or sub-files), and 3) local knowledge. When all appears harmonious, feel comfortable to upload to OSM.

Counties added

Alameda, Amador, Butte, Colusa, Contra Costa, El Dorado, Glenn, Lake, Los Angeles, Madera, Marin, Mariposa, Merced, Monterey, Napa, Orange, San Benito, San Joaquin, Santa Barbara, San Mateo, Santa Clara, Sierra Valley, Solano, Stanislaus, Tehama, Tulare, Yuba.

Counties without farm data

Del Norte, Humboldt, Trinity, Lassen, Plumas, Tuolumne, Calaveras, Mono, Inyo

Counties in progress

  • Sonoma


Primarily, Nathan Mixter.

SteveA made major contributions to the Monterey County effort. See for a historical perspective on how this was done.

  • If you are interested in helping by reviewing areas or have suggestion, please feel free to get in contact.