Re: Pixelated, Regional Topograpy Data

I notice the SRTM v.3 land data is now also being called "srtm plus" on tha=
t web page.

This is the link to the bathymetry that Joaquim is recommending=85

http://topex.ucsd.edu/WWW_html/srtm30_plus.html

The grid has a 30 arc second pitch, and while the land is at that resolutio=
n, the bathymetry has that resolution only at those relatively few location=
s where multi beam data was publicly available in 2008. At most locations t=
he bathymetry resolution might be analogized as correct but low pass filter=
ed at a resolution of a few arc minutes.

-jj



On Aug 11, 2014, at 2:50 PM, Joaquim Luis <[email protected]<mailto:jmfluis=
@GMAIL.COM>> wrote:

Use the SRTM+ (SRTM plus).
It's the best one of its class (30 sec resolution -- sometimes true, others=
 a bit less true)

Sent from my iDedo

No dia 11/08/2014, =E0s 11:41, Gregory Brenn <[email protected]<mailto=
:[email protected]>> escreveu:

I used SRTM, and the topography looks great.  I created a nice script.  Now=
 I want to add bathymetry data to the map that I overlaid earthquakes with.=
  Do you have any recommendations for where to get high-quality bathymetry =
data, such as from GEBCO?


On Aug 11, 2014, at 1:21 PM, Joaquim Luis <[email protected]<mailto:jmfluis=
@GMAIL.COM>> wrote:

On 11/08/2014, at 09:23, "Fielding, Eric J (329A)" <[email protected]=
A.GOV<mailto:[email protected]>> wrote:

The new SRTM v.3 has merged ASTER to fill voids. SRTM is better in almost e=
very location outside of voids.

And it takes 9 times less disk space

Joaquim


Sent from my iPadiola


++Eric

Sent from my iPhone

On Aug 11, 2014, at 12:17, "Becker, Joseph J." <[email protected]=
VY.MIL<mailto:[email protected]>> wrote:

I forgot to mention that we now combine the SRTM land data with the ASTER d=
ata which is also available for free. Outside of the US, the ASTER data is,=
 as I recall, the highest generally available resolution, however it is noi=
sy; e.g.; a tile near the Galapagos has a few points indicating ~7,000m ele=
vation on Isla Darwin.

We take all the land data we can get easily and block median it together fo=
r that reason. Simply taking an average would not work well. And the GMT to=
ols are fast so the extra computer time is negligible=85

-jj


On Aug 11, 2014, at 10:38 AM, JJ Becker <[email protected]<=
mailto:[email protected]><mailto:[email protected]=
avy.mil>> wrote:

I make the SRTM30_PLUS file(s) that were mention. If you=92d like to make y=
our own at a higher resolution here is what I do:

a bit of byte swapping on the HGT format file(s),
(optionally cat several altogether in a tmp file),
(optionally) block median the small tiles together to get the final resolut=
ion you would like,
and grid.


grd2xyz $cgiar -s -bo3 -V |
blockmedian -bi3 -bo3 -I$resolution -R$minX/$maxX/$minY/$maxY -C -V | \
xyz2grd -bi -G$grd  -R$minX/$maxX/$minY/$maxY -I$resolution -V


The block median options can be used to handle the possibly troubling issue=
s arising from the question of what location to pick when selecting the med=
ian height from a cloud of neighboring points (aka the center of the down s=
ampled pixel, the average location of the cloud, the location whose height =
happens to be the median, etc=85)

-jj

On Aug 9, 2014, at 3:13 PM, Gregory (Greg) Brenn <[email protected]<ma=
ilto:[email protected]><mailto:[email protected]>> wrote:

Ok,

That's great.  I downloaded an unzipped .hgt files, so what do you think wo=
uld be the best way to convert the .hgt files (I have 4 that I want to conv=
ert) into .grd files, then stich those files together?  Could I use xyz2grd=
 and then use grdpaste?

Thanks a lot for your help.
Greg


On Sat, Aug 9, 2014 at 2:44 PM, Fielding, Eric J (329A) <eric.j.fielding@jp=
l.nasa.gov<mailto:[email protected]><mailto:eric.j.fielding@jpl.=
nasa.gov>> wrote:
Yes, as Walter mentioned, the SRTM 3-arcsecond (~90 m) digital topography
is available for most of the Earth (up to 60 degrees N & S latitudes), and
it is much higher resolution than the ETOPO1 data that is 1-arcminute or
about 2 km spacing. The latest release is SRTM version 3.0. The Open
Topography website has a new service that will assemble the data and
provide the output in three formats
(http://www.opentopography.org/index.php/news/detail/srtm_version_30_global
_90m_and_united_states_30m_elevation_data_now_availab/<http://www.opentopog=
raphy.org/index.php/news/detail/srtm_version_30_global_90m_and_united_state=
s_30m_elevation_data_now_availab/>). The GeoTIFF files
are easy to convert to GMT .grd files with GDAL.

++Eric Fielding


-----Original Message-----
From: "Walter  Smith  (HF)" <[email protected]<mailto:walter.hf.smit=
[email protected]><mailto:[email protected]>>
Reply-To: World-Wide GMT Usage and Help Mailing List
<[email protected]<mailto:[email protected]><mailto:GMT-HEL=
[email protected]>>
Date: Saturday, August 9, 2014 11:04 AM
To: "[email protected]<mailto:[email protected]><mailto:GMT=
[email protected]>" <[email protected]<mailto:[email protected]=
AWAII.EDU><mailto:[email protected]>>
Subject: Re: [GMT-HELP] Pixelated, Regional Topograpy Data

=B3pscoast=B2 is defaulting to a low resolution coastline. Try adding -Df o=
r
check the usage message to get your highest option.

There is higher resolution topography than ETOPO1, such as SRTM3. You=B9ll
have to search around and you may have to assemble it from a few tiles
that you may have to download separately.

Walter

On Aug 9, 2014, at 1:50 PM, Gregory (Greg) Brenn <[email protected]<ma=
ilto:[email protected]><mailto:[email protected]>>
wrote:

Hello,

New user of GMT here, and I'm attempting to create a map of Costa Rica
and overlay coastlines and earthquake locations.  Here is my Script:

#!/bin/bash

clear

xyz2grd COSTARIC-6565.xyz -Gcostarica.grd -R-87/-84/9/11 -I2m -V

grdimage costarica.grd -JM12 -K -Cmy-topo.cpt -R-87/-84/9/11 >> map.ps<http=
://map.ps/>

pscoast -V -O -K -JM -R -W1 >> mappy.ps<http://mappy.ps/>

psxy loc.txt -JM12 -R-87/-84/9/11 -Sc.1 -G'45/59/100' -B1/1 -O >> map.ps<ht=
tp://map.ps/>
gv map.ps<http://map.ps/>



I am using a generic color palette which I can change easily, but the
coastlines are extremely low quality, and the topography is extremely
pixelated.

I look at images in papers, and there's extremely high quality
topographic images of COsta Rica, for example, as well as the coastlines
and bathymetry, but I have no idea where I can get this high-quality
data.  I have tried to get ETOPO data, but I cannot seem to find where
to get high-quality data.

So I guess my question is, is ETOPO1 the best place to get high-quality
topo data, because I cannot seem to figure out how to download data from
their website.  Also, would I need to download coastline data, as well?



Thanks,

Greg

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