1. Scan map.
Listed are nearby locations:
Scott Blueprint, 833-3912, 133 W 1st Ave., Mesa (used by Holloway)
ICM, 678-1978, 7600 N 16th St., Suite 205, Phoenix (used by Holloway and
Stone)
Commercial Blueprint, 967-1400, 20 E 7th St., Tempe
300 dpi grayscale is adequate for 7.5' topo quads. The scans should be in
uncompressed tiff format. This produces a ~45 MB image, so bring zip disks.
Most places require a pc-formatted zip disk. This can be read with our mac zip
drives with no conversion needed. Copy the file onto your MacData folder and
retain the zip disk as a backup of the original unaltered image.
2. Rotate image.
Make sure the map is aligned square. To check, zoom into 200-300% along the map
border, and scroll side to side and up to down. If the border veers out of
view, the image will need to be rotated, which is very likely. Launch Adobe
Photoshop (or Canvas). In Photoshop go to: Image-> Rotate
Canvas->Arbitrary, then enter the angle of rotation and direction. Angle
corrections will generally be from 0.05 to 0.1. Guides are useful to make sure
the map is aligned and to judge how much further rotation is needed. To place a
guide, zoom to map border, make sure rulers are on, hold the mouse button on
the ruler at the top of the image and a horizontal line will be dragged onto
the image and placed where ever you let go of the mouse button. The same can
be done with the vertical ruler to get a vertical guide. To get rid of these
guides go to View->Clear Guides.
3. Crop Image.
The image must be cropped so the upper left hand corner of the topo is the
upper left hand corner of the image. Hold down on the Marquee tool in the
toolbox (upper left corner, looks like a dashed line box) for more options and
select the tool the farthest to the right, it is a thick black box with a
diagonal through it. Click on the image and drag open a box on the image. The
box size/location can be adjusted by pulling on the tabs on the sides and
corners. When the box is in place, double click inside the box and Photoshop
will cut off the edges of the image. Guides are useful here as well as the
View->Snap To Guides feature.
4. Save image and ftp to Alai.
Once the image is rotated and cropped, make sure it is saved as a tiff
file in Photoshop (use the naming convention *.tif). Transfer file from Mac
desktop (or MacData) to Alai using Fetch. Start Fetch. Host is alai.la.asu.edu,
enter your user ID and password on Alai and click OK. Click on binary. Click on
Put File. Select the correct filename. Enter the filename you wish it to be
saved as on Alai (make sure this is in *.tif format). (It is generally best to
keep the same filenames to avoid future confusion). Click OK and watch the
little dog run until the file is transferred. A 35-40 MB file will take 2-3
minutes.
5. Import into Imagine.
Log in to Alai. Launch Imagine (Applications->ERDAS Imagine). Click on the
Import icon. Change Type menu to TIFF. Change Media menu to File. For input
file, click on the folder button and go to the Alai directory where your topo
image is located. (For successive files located in the same location, select
the Recent button.) Imagine will automatically create an output name as *.img.
Click OK. When finished processing, click OK, then close import window.
6. Georeference into Latitude/Longitude.
Open viewer. In viewer box go to File->Open->Raster, then enter the *.img
filename and click OK. Go to Utility->Layer Info. Note the width and height
in pixels.
In the ImageInfo dialog box, go to Edit->Change Map Model. Change the
Projection to Geographic (Lat/Lon), Units to degrees, and enter the upper left
X and Y coordinates and pixel sizes. The upper left X is the negative longitude
of upper left corner of map. The upper left Y is the positive latitude of upper
left corner of map. Latitude and longitude can be entered as DD MM SS and will
automatically be converted to decimal form. Pixel size X is 0.125/width in
pixels. Pixel size Y is 0.125/height in pixels. Click on OK.
The pixel size equations only work for 7.5' topo quads (7.5' = 0.125deg.). For
general use, this can be calculated by using the map scale to convert the
resolution of pixels/cm (on map) to pixels/m (on the ground). For example,
measure in the X direction 2.5' in inches on the map which equals 6.2 in. Pixel
size X is then equal to [(2.5'/6.2 in.)*(1 in./resolution)*(1deg./60')]. If
resolution is unknown go to original image in Photoshop->Image->Image
Size->Resolution.
In Utility->Layer Info, go to Edit->Add/Change projection. Projection
Type: Geographic Lat/Lon. Spheroid Name and Datum Name will be taken off the
paper topo map. For Central Arizona quads, it is commonly Clarke 1866 and NAD
27 respectively.
Close and reopen the now georeferenced image.
Place cursor in corners of image and check for accuracy. (X and Y coordinates
will be displayed in bottom left of viewer window.) This should be accurate to
0.000. If not, you will have to adjust the upper left hand corner or more
often, fudge the pixel width.
7. Reproject into UTM.
Open viewer. In viewer window go to File->Open->Raster, then enter the
*.img filename and click OK. Go to Raster->Geometric
Correction->Reproject. Toggle Parameters to Projection->Add/Change
Projection->UTM. Spheroid Name and Datum Name should be the same as for
Latitude/Longitude Projection. Zone is taken from the map. North for Northern
Hemisphere. Click OK. Click Apply. Increase the polynomial order (hitting Apply
each time) until RMS errors are 0.000000. Click on Resample Image button in the
Geo Correction Tools window (tilted shaded square). Click OK. When finished,
click OK on Resample Job Status window. Close Model Properties. Save as
different output file to distinguish from lat/lon (*UTM.img).
Close and reopen the now reprojected image.
Place cursor in corners of image and check for accuracy. This should be
accurate to 10 m. If not, recheck your inputs for spheroid, datum, zone, and
hemisphere, or try increasing polynomial order.