topic Re: Calculate Distance. in Python Questions

Calculate Distance.

RajP — Sat, 03 Oct 2015 12:06:10 GMT

Hello,

I need to update the distance field using the Pole_ID using Python script. From Pole_ID 0 to Pole_ID 1 and Pole_ID 1 to Pole_ID 2 and etc.

Kindly suggest me anyone.

Re: Calculate Distance.

DanPatterson_Retired — Sun, 12 Dec 2021 01:05:33 GMT

Inter-point distance

Do the following:

select Python parser
toogle on Show code block
paste the following in the Pre-logic Script Code block
and the last piece in the expression box

Pre-logic Script Code:

""" input shape field: returns the distance between points and its center
dist_between(!Shape!)    #enter into the expression box"""
x0 = 0.0;  y0 = 0.0
def dist_between(shape):
    global x0;  global y0
    x = shape.firstpoint.X; y = shape.firstpoint.Y
    if x0 == 0.0 and y0 == 0.0:
        x0 = x; y0 = y 
    distance = math.sqrt((x - x0)**2 + (y - y0)**2)
    x0 = x;  y0 = y
    return distance
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calculation field =

dist_between(!Shape!)
‍

where calculation field is your active field, it will show its name.

Make sure you have projected data and a double field or nothing will make sense.

Re: Calculate Distance.

DanPatterson_Retired — Sun, 12 Dec 2021 01:05:36 GMT

Cumulative Distance

If you want distance from the first point then use cumulative distance:

repeat the steps from above

Pre-logic Script Code:

""" input shape field: returns cumulative distance between points
dist_cumu(!Shape!)    #enter into the expression box"""
x0 = 0.0;  y0 = 0.0;  distance = 0.0
def dist_cumu(shape):
    global x0;  global y0;  global distance
    x = shape.firstpoint.X;  y = shape.firstpoint.Y
    if x0 == 0.0 and y0 == 0.0:
        x0 = x; y0 = y
    distance += math.sqrt((x - x0)**2 + (y - y0)**2)
    x0 = x;  y0 = y
    return distance
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

calculation field =

dist_cumu(!Shape!)
‍‍‍

Same caveats as above.

NOTE:

if you have 3 or more points selected, then it will calculate the values with just the selection.

Re: Calculate Distance.

NeilAyres — Mon, 05 Oct 2015 10:41:59 GMT

But, be aware that the attribute table is not guaranteed to be in PoleID order. Esp if you have done some editing.

Re: Calculate Distance.

DanPatterson_Retired — Sat, 10 Oct 2015 00:36:16 GMT

More calculations are shown here, if you didn't find the suggestions correct

Geometry: Points in the field calculator