Back To Week 2 and Tabular Data Structures
| On to Week 4 and Raster Analysis
Back To Week 2 and Tabular Data Structures
| On to Week 4 and Raster AnalysisOverview:
It is unlikely that you will need to perform many of these operations for producing data for LMS, but there is still some possibility tat you will. And what introduction to ARC/INFO would be complete without at least mentioning these?!
Here are the sample coverages: ring and box
Arcplot: items ring poly
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME INDEXED?
1 AREA 4 12 F 3 -
5 PERIMETER 4 12 F 3 -
9 RING# 4 5 B - -
13 RING-ID 4 5 B - -
17 DISP 1 1 I - -
Arcplot: items box poly
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME INDEXED?
1 AREA 4 12 F 3 -
5 PERIMETER 4 12 F 3 -
9 BOX# 4 5 B - -
13 BOX-ID 4 5 B - -
17 DESC 1 1 C - -
Arcplot: clear; mape ring; arcs ring; labeltext ring disp cc
Arcplot: clear; arcs box; labeltext box desc cc
Union
When 2 coverages are UNIONed, all features from both input coverages
are combined. All attribute items from the in_cover and union_cover are
included in the output.
Usage: UNION <in_cover> <union_cover> <out_cover> {fuzzy_tolerance}
{JOIN | NOJOIN}
Arc: union box ring boxuring
Arc: arcplot
Arcplot: mape boxuring
Arcplot: arcs boxuring
Arcplot: labeltext boxuring desc # uc
Arcplot: labeltext boxuring disp # lc
Note how the null areas from each of the input coverages are either null (for a character item) or 0 (for a numeric item). Also note how all input features have been retained, and new polygons have been created at intersections of input polygons.
Identity
The IDENTITY command maintains all features of the in_cover, but takes
features from the identity_cover that overlap with the in_cover.
Usage: IDENTITY <in_cover> <identity_cover> <out_cover> {POLY | LINE | POINT}
{fuzzy_tolerance} {JOIN | NOJOIN}
Arc: identity box ring boxiring
Arcplot: arcs boxiring
Arcplot: labeltext boxiring desc # uc
Arcplot: labeltext boxiring disp # lc
Intersect
The intersect command is similar to the other overlay commands, but
only areas which are common between the 2 inputs are included in the output.
The order of in_cover and intersect_cover does not matter.
Usage: INTERSECT <in_cover> <intersect_cover> <out_cover> {POLY | LINE | POINT}
{fuzzy_tolerance} {JOIN | NOJOIN}
Arc: intersect box ring ringxbox
Arcplot: arcs ringxbox
Arcplot: labeltext ringxbox desc # uc
Arcplot: labeltext ringxbox disp # lc
Update
UPDATE replaces overlapping parts of the input cover with features from
the update_cover. Only overlapping areas maintain attributes
Usage: UPDATE <in_cover> <update_cover> <out_cover> {POLY | NET}
{fuzzy_tolerance} {KEEPBORDER | DROPBORDER}
Arc: update ring2 box2 ringubox
Arcplot: arcs ringupbox
Arcplot: arcs ringupbox
Arcplot: labeltext ringupbox desc lc
Arcplot: labeltext ringupbox disp uc
Arc: update box2 ring2 boxupring Arcplot: arcs boxupring Arcplot: labeltext boxupring disp uc Arcplot: labeltext boxupring desc lc
Clip
CLIP clips out parts of the in_cover with the convex hull of the clip_cover.
Only attributes from the in_cover are retained.
Usage: CLIP <in_cover> <clip_cover> <out_cover>
{POLY | LINE | POINT | NET | LINK | RAW} {fuzzy_tolerance}
Arc: clip box ring boxcring
Arcplot: arcs boxcring
Arcplot: labeltext boxcring desc lc
Arcplot: labeltext boxcring disp uc
disp does not exist within BOXCRING.pat
Arc: clip ring box ringcbox Arcplot: arcs ringcbox Arcplot: labeltext ringcbox disp uc Arcplot: labeltext ringcbox desc lc desc does not exist within RINGCBOX.pat
Whenever a buffer is performed, an attribute is added to the out_cover.pat called "inside." the value of inside = 100 for areas within the buffer and 1 for areas outside the buffer. See the final sample below for an example of this.
Here are a few examples of some simple, constant-width buffers.
Usage: BUFFER <in_cover> <out_cover> {buffer_item} {buffer_table}
{buffer_distance} {fuzzy_tolerance} {LINE | POLY | POINT | NODE}
{ROUND | FLAT} {FULL | LEFT | RIGHT}
Arc: buffer point_test point_buf # # .15 # point
Arcplot: arcl point_buf 2
Arcplot: markerset water
Arcplot: pointmarkers point_test 102
Arc: buffer line_test line_l_f # # .2 # line flat left Arcplot: lineset carto Arcplot: arcs line_test Arcplot: arcl line_l_f 3 Arcplot: arcs line_test
Arc: buffer box box_buf # # .2 # poly Arcplot: arcs box Arcplot: arcl box_buf 4
Here are a few examples of how overlay commands can answer spatially-related questions.
Question: What is the road density in each age class for Pack Forest (ft/ft^2)?
Coverages:
rds2 = roads coverage (arc)
(ftp://ftp.u.washington.edu/public/packfor/gis/data/rds2.e00)
tty4 = timber type coverage (net = arc & poly attributes)
(ftp://ftp.u.washington.edu/public/packfor/gis/data/tty4.e00)
To import these coverages, place the interchange (.e00) files in a directory and use the IMPORT command, e.g.,
Arc: import cover rds2 rds2
Once you have imported the coverages, make sure to DESCRIBE them so you will know what units to report in.
Steps:
Arc: frequency tty4.pat f_tty4_age_area Enter Frequency item names (type END or a blank line when done): ================================================================ Enter the 1st item: age_cl_1998 Enter the 2nd item: end Enter Summary item names (type END or a blank line when done): ============================================================== Enter the 1st item: area Enter the 2nd item: end
Arc: intersect rds2 tty4 rds_tty line
Arc: frequency rds_tty.aat f_rds_tty_age_length Enter Frequency item names (type END or a blank line when done): ============================================================ Enter the 1st item: age_cl_1998 Enter the 2nd item: end Enter Summary item names (type END or a blank line when done): ============================================================== Enter the 1st item: length Enter the 2nd item: end
Arc: additem f_rds_tty_age_length f_rds_tty_age_length density 4 12 f 6
Arc: relate add Relation Name: road_density Table Identifier: f_tty4_age_area Database Name: info INFO Item: age_cl_1998 Relate Column: age_cl_1998 Relate Type: linear Relate Access: ro Relation Name: <CR> Arc: tables Enter Command: sel f_rds_tty_age_length Enter Command: calc density = length / road_density//area Enter Command: li Record CASE# FREQUENCY AGE_CL_1998 LENGTH DENSITY 1 1 368 0-10 107600.778669 0.001381 2 2 157 10-20 55187.060429 0.001581 3 3 2 100-110 413.625120 0.001304 4 4 53 190-200 14149.321093 0.002787 5 5 20 20-30 12195.034552 0.001324 6 6 21 30-40 3848.984411 0.001816 7 7 15 50-60 4128.005425 0.001835 8 8 238 60-70 74847.994910 0.001316 9 9 98 70-80 20146.499639 0.002365 10 10 8 90-100 3940.154343 0.003305
This table can easily be exported as ASCII text and then imported to a spreadsheet, external database, or word processor. We will get practice in exporting text in Week 8.
These exercises are limited to the area of Pack Forest. Visit Pack's GIS Web site to download data sets.
How much area is in each slope class, for each 10-year age class?
Get the coverage slp_4
via anonymous ftp.
How much area is in 60-80 year-old stands within 200 feet of stream types
1-3?
(Hint: you may want to add a buffer item to the stream cover's AAT.)
Back To Week 2 and Tabular Data Structures
| On to Week 4 and Raster Analysis