Re: Lat/Lon waypoints for GPS

Keith wrote:
In message <fFTAwIBlzK1EFwB6@xxxxxxxxxxxxxxxxxx>, Keith
<keith@xxxxxxxxxxxxxxxxxx> writes
In message <jz1Bg.257$yG1.208@xxxxxxxxxxxxxxxxxxxx>, Dennis Pogson
<dennis_nospampogson@xxxxxxxxxxxx> writes

I just downloaded the full-size NASA MrSid image from
https://zulu.ssc.nasa.gov/mrsid/mrsid.pl There were no clouds on
this, and the image is startlingly clear and well-defined. The
earth map reference is N-49-20_2000 ( you have to keep zooming in
until the ref. numbers show, then click on Select Image and click
on the above sector in the map.

This will bring up a close-up window of the area and you can then
download the whole area (about 180MB). To view and use sections of
this you need the free MrSid viewer from LizardTech,
http://www.lizardtech.com/download/ which will enable you to
extract sections as tiff files and use them in various nav.
programs.

At full scale magnification and good eyesight you can see the paddy
fields (but not the rice shoots!) in Thailand.


Dennis, I've downloaded the viewer from LizadTech but I cannot find a
method of dowloading the specific area from MrSid.

Should I <Select Image> <File> <Save> ?

What's the magic sequence?

Zoom in by repeatedly single-clicking on the rectangle of the area you want,
until the required image is on screen and it's reference number shows.

Click on the radio button "select image", then single-click on the rectangle
containing the image you want.

When the download screen appears, simply click on "Download MrSid image".
There is also the ability to view sections of the image at higher
magnifications, but I usually ignore this. The images vary in size from
around 50MB to 160MB, so unless you have an 8mb Broadband connection, be
patient!

You can use the MrSid viewer from LizardTech to view and magnify the images
and sections thereof. The images are already geo-referenced as Tiff images.

Ozi explorer can read these images directly if you download the file,
OziMrSid.dll, from their website. These images are HUGE, and take a while
even for Ozi to load.

I usually use the MrSid viewer from Lizardtech to save sections of the image
and calibrate these sections in Ozi, usually to WGS84 datum. The full-size
originals are usually calibrated to NAD27Conus on downloading, and most of
my reference calibration data is to WGS84, hence the changes.

As I said in an earlier post, there are areas where the maps join which
require care as the coastline can be distorted, and you can't see this,
thanks to some clever jiggery-pokery by NASA, but the bulk of the maps are
pretty accurate.

I have no connection with NASA. I did make a bid for it in the early sixties
but Kennedy refused to budge!

Dennis.






.

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