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Structure Points in Geological mapping

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#1
Kalai Selvan

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In any geological map, faults have a prominance, i have interacted with a lot of geologist and all of them give different perception on faults. Was quite impressed to know different details from different geo but all the answers were interesting.

Again these geological maps have always put me under deep thinking, like structure points with different symbols, like wise outcrop points with different representation and offcourse they have their own important.

My ? is What exactly does
Incline
Vertical
Horizontal Points denote, can someone let me know on this by looking @ the attached snap shot.


Thanks!!!!
GISGURU

Attached Files


Thanks and Regards
Kalai Selvan


#2
Tommo

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Hi GISGURU

Your symbols represent the orientation of a geological feature. They represent the strike and dip. The strike is the azimuth of the intersection of the feature with a horizontal plane. The dip is the angle from horizontal perpendicular to the strike line, pointing downslope.

For the first symbol - Inclined - the long arm represents the strike and the short arm is pointed down dip on the strata. The long arm should be oriented to the strike azimuth.

As no short arm can be displayed for horizontal or vertical features, the alternative symbols are provided.

Hope that made some sort of sense!

Cheers
Tommo

#3
MountainCartography

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Without having a degree in Geology or even a basic Geology 101 course, strike and dip of bedding, faults, cleavage, foliation, or any other mappable geologic plane or lineage, etc. is fairly hard to explain to a layman, and often times to many geologists whom indicate that they are trained as such. Without a compass or stereograph it is even harder to explain, but I'll also give it a whirl and add to Tommo's explanation...

Take a book and prop it up on an incline. Strike is a bearing of any line where an imaginary horizontal plane intersects the inclined surface. Dip is always 90-degrees to strike, which points in the direction of downward inclination of the book. The dip inclination amount is generally indicated by the dip angle (inclination).

The vertical bedding symbol indicates that dip is 90-degrees straight into the earth, and the horizontal symbol indicates that there is zero dip (and subsequently zero strike).

There are of course other "variations" to a structural strike and dip symbol (such as rake), though again, you should look into a basic course in Geology. Even then, depending on the college or university, the professor might not cover advanced geologic mapping technique in a basic geologic course.

Associated data for strike and dip should accompany any field map. The international rule of thumb for digital mapping is to list strike as a singular number between o and 360-degrees. The dip direction should always be 90-degrees right of the strike. This is called the right-hand rule. So, (for the northern hemisphere of the earth) if you had a strike of 045-degrees and a dip of 30-degrees, the strike line on the map should be oriented northeast and the dip line should point to the southeast. If the strike was posted as 225-degrees, the dip should point to the northwest.

See also wikipedia: http://en.wikipedia..../Strike_and_dip

For examples of at least USGS geologic symbol representations, lithologic fill patterns, standard colors, etc, etc, visit:

http://ngmdb.usgs.go...td/download.php

There are of course other national government websites similar to this one (Canada for instance has many good web sources for geologic and other geographic cartography standards). It would also be a good idea to check with the project geologist to determine which standard she or he is using, and hope that they are using a standard of some flavor.

Even if you do plan to continue to make maps for a as low as $10 per hour... I hope you at least do it correctly.
"scale rules our lives" ~ Jim Barnes, circa 1996, somewhere out on the tiaga of Alaska

#4
Kalai Selvan

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Without having a degree in Geology or even a basic Geology 101 course, strike and dip of bedding, faults, cleavage, foliation, or any other mappable geologic plane or lineage, etc. is fairly hard to explain to a layman, and often times to many geologists whom indicate that they are trained as such. Without a compass or stereograph it is even harder to explain, but I'll also give it a whirl and add to Tommo's explanation...

Take a book and prop it up on an incline. Strike is a bearing of any line where an imaginary horizontal plane intersects the inclined surface. Dip is always 90-degrees to strike, which points in the direction of downward inclination of the book. The dip inclination amount is generally indicated by the dip angle (inclination).

The vertical bedding symbol indicates that dip is 90-degrees straight into the earth, and the horizontal symbol indicates that there is zero dip (and subsequently zero strike).

There are of course other "variations" to a structural strike and dip symbol (such as rake), though again, you should look into a basic course in Geology. Even then, depending on the college or university, the professor might not cover advanced geologic mapping technique in a basic geologic course.

Associated data for strike and dip should accompany any field map. The international rule of thumb for digital mapping is to list strike as a singular number between o and 360-degrees. The dip direction should always be 90-degrees right of the strike. This is called the right-hand rule. So, (for the northern hemisphere of the earth) if you had a strike of 045-degrees and a dip of 30-degrees, the strike line on the map should be oriented northeast and the dip line should point to the southeast. If the strike was posted as 225-degrees, the dip should point to the northwest.

See also wikipedia: http://en.wikipedia..../Strike_and_dip

For examples of at least USGS geologic symbol representations, lithologic fill patterns, standard colors, etc, etc, visit:

http://ngmdb.usgs.go...td/download.php

There are of course other national government websites similar to this one (Canada for instance has many good web sources for geologic and other geographic cartography standards). It would also be a good idea to check with the project geologist to determine which standard she or he is using, and hope that they are using a standard of some flavor.

Even if you do plan to continue to make maps for a as low as $10 per hour... I hope you at least do it correctly.


Thanks Mountain,
Very informative answer, you are right in saying "Even if you do plan to continue to make maps for a as low as $10 per hour... I hope you at least do it correctly" Finally no one wants a scrap after paying as low as $10.
While capturing these features, doesn't really need to have a geology degree, but if you are well versed in adding the information in the right way, that indeed will produce what is required. coz civil engineers engaged in geological mapping produce better maps than a degree holder in geology. I hope you will agree with me.
Anyway good explaination Mountain.

Cheers!!!
GISGURU

Thanks and Regards
Kalai Selvan





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