(3) Bypass impossible.
The obstacle can only be crossed by rebuilding, or using special
l. Critical point: This symbol is used to identify points or symbols on an overlay that do not have a
military symbol. Used to identify locations discussed in the legend.
m. Bridge symbol: This symbol is used to identify a bridge or its measurements. Remember the O
W L formula. O W L - O, overhead: W, width; and L, length (see Appendix A).
(1) On the left side is the overhead clearance of the bridge.
(2) The bottom center is the width of the traveled way.
(3) The number on the right-hand side is the overall length of the bridge.
n. Ford crossing: This symbol is used to report information for a crossing of a river or a stream
(see Appendix A, page A-4).
(1) Easy approach: A straight line shows an easy approach to a crossing. Examples are flat
stream bed with no banks, or a stream or river with built-in driveway approaches.
(2) Difficult approach: The jagged line shows a difficult approach. For instance, a stream bed
with large rocks along the bank or a stream or river with high ledge type banks that may have to be
knocked down to cross. Another example is a river bank with debris, trees, or barriers installed to stop
traffic or erosion.
(3) Serial number: The serial number can be reported on the overlay if engineers have already
been at the location and have posted a sign with the information that you are about to record. Serial
numbers are assigned by HTH. If there are no signs posted, put a question mark in this portion of the
(4) Type of fording: Record whether this is a vehicle crossing, pedestrian, or both.
(5) Velocity of stream: Record the streams velocity if the stream is deep enough to record it.
(6) Seasonal limitations: The letter X indicates no seasonal limitation except for limited sudden
flooding. Letter Y is used to report seasonal limitations. Example for letter Y is that it floods year round
or at least the majority of the year. Example for X is it only floods once or twice a year.
(7) Length across stream: The distance of the stream bed that is capable of carrying vehicles or
personnel across the stream.