********** CCaalliiffoorrnniiaa DDiiggiittaall RRaasstteerr GGrraapphhiiccss **********
********** CCaalliiffoorrnniiaa DDiiggiittaall RRaasstteerr GGrraapphhiiccss **********
******** AAbbssttrraacctt ********
Digital Raster Graphics are provided online by the _C_a_l_i_f_o_r_n_i_a_ _S_p_a_t_i_a_l
_I_n_f_o_r_m_a_t_i_o_n_ _L_i_b_r_a_r_y_ _(_C_a_S_I_L_) .
A DRG is useful as a source or background layer in a GIS, as a means to perform
quality assurance on other digital products, and as a source for the collection
and revision of DLG data. DRGs can also be merged with other digital data, e.g.
DEMs or DOQs, to produce a hybrid digital file.
The maps are organized into 1x1 degree blocks covering the state. Within these
blocks are the individual maps and ancillary data. Maps are named by their USGS
identifier as described in _S_t_a_n_d_a_r_d_i_z_e_d_ _D_a_t_a_ _S_e_t_ _N_a_m_e_s .
******** SSeerriieess IInnffoorrmmaattiioonn ********
There are multiple series of DRGs for different scales. The 1x2 degree series
is at a scale of 1:250K. The 30x60 minute series is at a scale of 1:100K, and
the 7.5 minute series is at 1:24K. Additionally, there are some 1:25K scale
maps that are included in this distribution as belonging to the 7.5 minute
series.
For the 1x2 degree series, there are 41 images covering the state of California
and immediately adjacent areas. These DRGs were originally obtained from the
California Department of Fish and Game (DFG).
For the 30x60 minute series, there are 127 images covering the state of
California and immediately adjacent areas. These DRGs were originally obtained
from the California Department of Fish and Game (DFG).
For the 7.5 minute series, there are 2853 images covering the state of
California and immediately adjacent areas. Statewide DRG production was
performed by the State of California, Stephen P. Teale Data Center, GIS
Solutions Group (Teale). Additional acknowlegdements include: Governor's Office
of Emergency Services (OES): compilation of DRG quad dates and other
attributes; California Department of Fish and Game, Information Technology
Branch: non-standard quad boundaries, quad currentness year information and
enhanced index compilation.
******** PPrroojjeeccttiioonn IInnffoorrmmaattiioonn ********
The Digital Raster Graphic (DRG) is a raster image of a scanned USGS
topographic map including the collar information. The source maps for DRGs were
georeferenced to the UTM grid, but images DRGs for California are available in
Albers equal area projection as well. Most DRGs were originally in the NAD27
datum, but have been converted and are available in NAD83 as well.
Information about the projection used by the DRGS can be found at _C_A_ _P_r_o_j_e_c_t_i_o_n
.
******** OObbttaaiinniinngg DDRRGGss ********
All California Digital Raster Graphics are available at _f_t_p_:_/_/
_c_a_s_i_l_._u_c_d_a_v_i_s_._e_d_u_/_c_a_s_i_l_/_g_i_s_._c_a_._g_o_v_/_d_r_g, or _h_t_t_p_:_/_/_c_a_s_i_l_._u_c_d_a_v_i_s_._e_d_u_/_c_a_s_i_l_/
_g_i_s_._c_a_._g_o_v_/_d_r_g .
Various mirrors sites of the CaSIL data also provide DRGs, such as the
Sacramento Mirror: _f_t_p_:_/_/_c_a_s_i_l_-_m_i_r_r_o_r_1_._c_e_r_e_s_._c_a_._g_o_v_/_c_a_s_i_l_/_g_i_s_._c_a_._g_o_v_/_d_r_g and
_h_t_t_p_:_/_/_c_a_s_i_l_-_m_i_r_r_o_r_1_._c_e_r_e_s_._c_a_._g_o_v_/_c_a_s_i_l_/_g_i_s_._c_a_._g_o_v_/_d_r_g .
Map interfaces are available at _h_t_t_p_:_/_/_c_a_s_i_l_._u_c_d_a_v_i_s_._e_d_u_/_m_a_p_s_u_r_f_e_r_/ and _h_t_t_p_:_/_/
_i_m_s_._g_i_s_._c_a_._g_o_v_/_w_e_b_s_i_t_e_/_c_a_s_i_l_/_d_r_g_q_u_a_d_s_/_v_i_e_w_e_r_._h_t_m .
******** DDaattaa OOrrggaanniizzaattiioonn ********
The DRG data at CaSIL are organized by directories. The directories are named
based on the series (C|F|0), projection(Albers NAD27|Albers NAD83), and type
(trimmed|untrimmed|mosaic).
In the case of the 7.5 Minute (O) Series, the DRGs are further subdivided based
on the USGS quad identifier (ie. 37122).
Users of web browsers can click on the desired quad on the client side image
map to directly retrieve the appropriate GeoTiff file. A tooltip will show up
to help identify the actual quad on the client side image map.
******** FFuurrtthheerr IInnffoorrmmaattiioonn ********
Further information about the California DRGs can be found at _A_b_o_u_t_ _C_a_l_i_f_o_r_n_i_a
_D_R_G_s .