topic Re: Generate hourly perimeters from daily data in ArcGIS Pro Questions

Generate hourly perimeters from daily data

RZara — Mon, 11 Oct 2021 04:32:04 GMT

Hi all,

I have spatial-temporal point data. The point data represents locations at various times over the course of a couple of days. I would like to predict locations at fixed hourly intervals within a day (e.g every hour or every 4 hours) as polygons. All research has been leading back to the idea of using interpolation but I'm unsure of how to maneuver the tool for this purpose. Any recommendations on how to go about this?

Thanks for any input!

Best,

Rachel

Re: Generate hourly perimeters from daily data

JohannesLindner — Mon, 11 Oct 2021 08:27:58 GMT

Couldn't you just use the convex hull of all points in the same interval?

import datetime # variables points_fc = "PointFC" date_field = "DateField" time_interval_minutes = 60 polygon_buffer = 100 # read shape and date data = [r for r in arcpy.da.SearchCursor(points_fc, ["SHAPE@", date_field], sql_clause=(None, "ORDER BY " + date_field))] # construct time bins start_time = data[0][1] end_time = data[-1][1] time_bins = [start_time] while time_bins[-1] < end_time: time_bins.append(time_bins[-1] + datetime.timedelta(minutes=time_interval_minutes)) # create output fc sr = arcpy.Describe(points_fc).spatialReference polygons = arcpy.management.CreateFeatureclass("memory", "polygons", "POLYGON", spatial_reference=sr) arcpy.management.AddField(polygons, "StartTime", "DATE") arcpy.management.AddField(polygons, "PointCount", "LONG") # fill output fc with arcpy.da.InsertCursor(polygons, ["SHAPE@", "StartTime", "PointCount"]) as cursor: for b in range(len(time_bins)-1): # get points that belong to the interval t0 = time_bins[b] t1 = time_bins[b+1] points = [d[0].firstPoint for d in data if d[1] >= t0 and d[1] < t1] # if there are points in the interval if points: # change list of point geometries to multipoint geometry multipoint = arcpy.Multipoint(arcpy.Array(points)) # get the convex hull, buffer to prettify polygon = multipoint.convexHull().buffer(polygon_buffer) # insert cursor.insertRow([polygon, t0, len(points)])

Re: Generate hourly perimeters from daily data

JohannesLindner — Mon, 11 Oct 2021 09:10:07 GMT

I think I misunderstood your question...

The code above shows you the locations in a certain time interval. You want to know the probable locations in a time interval during a random day. Basic idea still applies:

from datetime import date, time, timedelta # variables points_fc = "PointFC" date_field = "DateField" time_interval_minutes = 60 polygon_buffer = 100 # read shape and date data = [list(r) for r in arcpy.da.SearchCursor(points_fc, ["SHAPE@", date_field])] for d in data: d.append(datetime.combine(date.today(), d[1].time())) # construct time bins start_time = datetime.combine(date.today(), time(0, 0)) end_time = start_time + timedelta(days=1) time_bins = [start_time] while time_bins[-1] < end_time: time_bins.append(time_bins[-1] + timedelta(minutes=time_interval_minutes)) # create output fc sr = arcpy.Describe(points_fc).spatialReference polygons = arcpy.management.CreateFeatureclass("memory", "polygons", "POLYGON", spatial_reference=sr) arcpy.management.AddField(polygons, "StartTime", "TEXT") arcpy.management.AddField(polygons, "PointCount", "LONG") # fill output fc with arcpy.da.InsertCursor(polygons, ["SHAPE@", "StartTime", "PointCount"]) as cursor: for b in range(len(time_bins)-1): # get points that belong to the interval t0 = time_bins[b] t1 = time_bins[b+1] points = [d[0].firstPoint for d in data if d[2] >= t0 and d[2] < t1] # if there are points in the interval if points: # change list of point geometries to multipoint geometry multipoint = arcpy.Multipoint(arcpy.Array(points)) # get the convex hull, buffer to prettify polygon = multipoint.convexHull().buffer(polygon_buffer) # insert cursor.insertRow([polygon, t0.strftime("%H:%M"), len(points)])

Re: Generate hourly perimeters from daily data

RZara — Tue, 12 Oct 2021 02:21:30 GMT

Johannes,

Thank you for taking the time to assist. I understand that you described that the solution would generate polygons representing locations in a time interval during a random day. May you clarify if it could generate a feature class representing sub-daily time intervals from the daily data? I want to examine time intervals within the course of time that the data takes place (e.g. dataset took place over a 3-day time period and I want values for every 4 hours within those 3 days).

Re: Generate hourly perimeters from daily data

JohannesLindner — Tue, 12 Oct 2021 05:40:43 GMT

Sorry, I find it hard to describe, as English isn't my first language. Hopefully the illustration helps...

Imagine you have location data over two days (red and blue points).

The first code sample will give you the polygons on the left side: one polygon for each time interval on each day. "Where were you on day 1, interval 2?"

The second code sample will give you the polygons on the right side: one polygon for each time interval on all observed days. "Where were you on any day, interval 2?"

Re: Generate hourly perimeters from daily data

RZara — Mon, 18 Oct 2021 20:16:17 GMT

The illustration was very helpful. I'll give it a try.