How to use USGS DOQQs from a county CD-ROM with ArcExplorer ( a free GIS data viewer )
Follow these steps:
Copy the DOQQ image (*.nec, nwc, sec, or swc) and its header file (*.neh, nwh, seh, or swh) to your hard drive. Rename the image file so that is is now image.jpg where image can be any filename.
Using image-editing software transform the .jpg file to a .tif file. This will probably increase the the size of the file by about 4X.
Create an empty text file called image.tfw. (This filename needs to match the filename of the image in Step 1). The file should contain 6 lines when you are done. The first four lines can be entered now.
Open the the DOQQ header file you copied to your hard drive. The file name (*.neh, nwh, seh, or swh) should match the original image file name (ex. O3307807.sec for the image and O3307807.seh for the header).
Copy the last two numbers from the 3rd Record. Paste these coordinates into image.tfw. These are the coordinates of the first pixel in the image (the top lefthand or northwest pixel. Edit the coordinates so that they are no longer in scientific notation (ex. 3.759055555000000D+6 will be 3759055.555000000). The first of the two coordinates is line 5 in image.tfw and the second coordinate is line 6 in image.tfw
You have now created a world file which will register the .tif image in Universal Transverse Mercator (UTM) coordinates in the NAD27 datum. This will allow you to overlay the DOQQ on a DRG image. If you use the two numbers preceding the last two in Record 3, the image will be registered in Universal Transverse Mercator (UTM) coordinates in the NAD83 datum.