Step 1.
County street download does not include alley.
Alley also have address. sometime, alley address is same as front door address.
sometime, alley (back door) is on another street.
alley address will help police officer quickly access back door from alley instead of front door.
building safety department, build permit require alley address if they have.
https://data.lacounty.gov/datasets/lacounty::address-street-lines/about
click download button for street only, not alley
Step 2.
click download button you get street only, but not alley,
Step 3.
where is alley?
blue line are alley.
Step 4.
how to download alley?
install plugin
Step 5.
click map preset,
click CTR
Step 6.
input city name,
click run button
Step 7.
after run button complete, you will get road layer,
Step 8.
Note, this is open street map format, you will need to
export road layer to shape file ( which ESRI software can use it later)
Step 9.
Step 10.
yellow line include all linework, street, alley, etc... it is shape file format, can be load into arcgis pro later
Step 11.
load into arcgis pro
open attribute table,
alley don't have street name,
sort by street name, select all line that don't have street name, see yellow box
Step 12.
export these selected into another shape file named alley
Step 13.
this is raw alley, have all line work, may not be a real alley,
down stream process will refine it. to only alley.
Step 14.
Step 15.
Step 16.
Step 17.
Step 18.
Step 19.
Step 20.