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Dan,
These links might be of help:
Regards,
----- Original Message -----
Sent: Thursday, 27 January, 2000 02:38
PM
Subject: California(CA)
Soil/Liquefaction/MMI Data
Tim
Any idea where to get detailed soil, MMI or
liquefaction data for CA? I've
found localized information for the
Bay Area & LA, but they're different.
Looking for stuff that covers the
whole state, or is at least consistent.
I've looked through the Div. Mines
& Geology & ABAG sites, but none of it is
good
state-wide.
Dan
----- Original Message -----
From: Tim Warman
<[EMAIL PROTECTED]>
To:
Mapinfo-L <[EMAIL PROTECTED]>
Sent: Thursday,
January 27, 2000 2:07 PM
Subject: MI NAD83 and NAD27
> I'm
still trying to track down the source of the mismatch between
several
of
> my data sets, and in doing so have generated several new
questions:
>
> 1. Does anyone know whether USGS DLGs for
California (both the 1:24,000
and
> 1:100,000 scales) were originally
created in NAD83 or NAD27? The original
> paper quad sheets I've seen
(1:24,000) are in NAD27, with a description in
> the margins of the
offset to the NAD83 grid.
>
> 2. Is anyone using the TopoDepot
CDs? I've noticed that when I create a
map
> using the NAD27 datum
and print it at 1:24,000 along with the 7.5 minute
> quad boundary file
from the USGS (which is in "unprojected" lat long), the
> map elements
line up very well with the paper versions of the quad sheets
> (using
the USGS boundary file to align the two maps on a light table).
>
However, the same TopoDepot map created in NAD83 shows the
characteristic
> NAD27-NAD83 offset (usually a few hundred feet) from
the paper version.
This
> leads me to believe that the TopoDepot
software simply changes the
coordsys
> settings, but leaves the
actual coordinates the same, i.e. doesn't
actually
> reproject the
data. Anyone else seeing this?
>
> 3. Along these same lines, I've
received several GIS data sets (in NAD83)
> from large public agencies
in southern California, and these data sets
line
> up with
TopoDepot's seemingly erroneous NAD83 maps (see point 2). At least
> one
of these GIS data sets was originally created in NAD27 and later
>
"converted" to NAD83, leading me to believe that these public agency
GIS
> data sets also not reprojected properly.
>
> I'd love
to hear from Cliff Mugnier, the MapInfo-l projection and datum
>
demigod, on this one.
>
> TIA, and I promise to write a complete
summary when I get to the bottom of
> this.
>
_____________________________
> Tim Warman
> Geologist & GIS
Specialist
> Richard C. Slade & Associates
> North Hollywood,
CA
> (818) 506-0418
>
>
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