topic Calculate distance between consecutive points in Data Management Questions

Calculate distance between consecutive points

KarrenO_Neill — Thu, 06 Mar 2014 23:42:20 GMT

Hi
I wish to calculate the distance between consecutive points in a feature class.
I tried using the following code in the "Pre-Logic VBA Script Code" box in the Field Calculator dialog -

static x0 as double, y0 as double ' Previous location
dim pPoint as IPoint
set pPoint = [Shape]

x = pPoint.X
y = pPoint.Y
d = sqr((x - x0)^2 + (y - y0)^2) ' Distance
x0 = x
y0 = y

but it doesn't work. Does anyone have any suggestions? Thanks for any help anyone can give me.

Re: Calculate distance between consecutive points

RichardFairhurst — Sat, 11 Dec 2021 17:52:36 GMT

Hi
I wish to calculate the distance between consecutive points in a feature class.
I tried using the following code in the "Pre-Logic VBA Script Code" box in the Field Calculator dialog -

static x0 as double, y0 as double ' Previous location
dim pPoint as IPoint
set pPoint = [Shape]

x = pPoint.X
y = pPoint.Y
d = sqr((x - x0)^2 + (y - y0)^2) ' Distance
x0 = x
y0 = y

but it doesn't work. Does anyone have any suggestions? Thanks for any help anyone can give me.

VB Script at 10.0 or later cannot use the DIM statement to create Point variables anymore (or any other variable type other than Variant). You have to use Python for all geometry field calculations from now on.

Here is my attempt based on an adaptation of the autoincrement calculation.

Parser: Python

Use Codeblock: checked

Pre-Logic Script Codeblock:

x0 = 0.0
y0 = 0.0
def distance(x, y):
 global x0
 global y0
 if x0 = 0.0 and y0 = 0.0:
  x0 = x
  y0 = y
 d = math.sqrt((x - x0)**2 + (y - y0)**2) # Distance
 x0 = x
 y0 = y
 return d

Expression: distance(!shape.Centroid.X!, !shape.Centroid.Y!)

I am assuming the first point should give a distance of 0, so I set an invalid coordinate that I know will not be in your data and replace that impossible value with the first point value. If 0,0 is a possible coordinate change the initial x0 and y0 values outside the def to a known invalid point location and change the if condition to match it.

Re: Calculate distance between consecutive points

KarrenO_Neill — Mon, 10 Mar 2014 21:54:41 GMT

Hi Richard,
great! thanks for that. One slight error the if statement should read - if x0 == 0.0 and y0 = =0.0:
Very much appreciated!

Re: Calculate distance between consecutive points

RichardFairhurst — Mon, 10 Mar 2014 22:21:21 GMT

Hi Richard,
great! thanks for that. One slight error the if statement should read - if x0 == 0.0 and y0 = =0.0:
Very much appreciated!

I always forget that. I am a VB Script guy more than a Python guy and that trips me up all the time. Anyway, glad you got it working.

Re: Calculate distance between consecutive points

RichardFairhurst — Wed, 19 Mar 2014 14:45:11 GMT

Hi Richard,
great! thanks for that. One slight error the if statement should read - if x0 == 0.0 and y0 = =0.0:
Very much appreciated!

I only write VB Script calculations if I don't have to use Python, so when I have to use Python I always forget that = is not == (there is no such thing as == in VB Script). So I normally make that mistake in all the code examples I write from memory on the Forum that I have not actually run. In any case, glad it works for what you needed.