[GIS] Creating Point Transects along line using ArcMap

arcgis-10.1arcgis-desktoparcmaptransects

I would like to create a point shapefile that will contain sampling points along, and perpendicular to either side of a track route that I have as a line feature in ArcMap 10.1. The points on the track will be every 50m along the line with the perpendicular points 10m either side of that.

Is there a tool that I can use to generate my points to save me placing over 300 points manually?

Attached is a image prepared in powerpoint of what I am trying to achieve.

enter image description here

As you can see I would like to place points every 50m along the route of an existing track that is present in real life and has been digitised into ArcMap . The points perpendicular to the track points are 10m either side of the point.

I did manage to get a rough plan of the locations by using a bit of a long winded route and a free add in tool called ETGeo Wizard. This method involved the following steps:

Generate a 10m buffer around the track route polyline;
Convert the buffer polygon to a polyline;
Split the rounded ends off the polyline (i.e the original rounded edges of the buffer) leaving two lines 10m from the track route polyline;
Use ETGeo Wizard to place points every 50m along the polyline;

This method does give me the points but there is a lot of error meaning a lot of manual editing. It is also quiet a time consuming method of generating my points given that I have lots of track sections to place points on. I would therefore like to find a way to generate the points automatically using a tool or script.

Best Answer

you can follow these steps:

Generalize line
Densify using 50m with densify by distance parameter.
buffer the line with flat option with 10m as distance.
get the polygon result vertices using Feature vertices tool

If I haven't really understood your question, can you provide a simple drawing to explain the problem clearly.

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[GIS] Offsetting points perpendicular to line using ArcMap

I found a way! I used a couple of different sources and manipulated the script to fit my needs (mostly from gotanuki on StackExchange). A variation of this is already on the site, but the of data that I was using is different. In case someone else runs into this issue, this is the solution I used:

# Define orientation (start, mid, end) and draw Matchlines function
# This function is defined before it is called
def orientMatchlines(feat,ix,iy):
        # If the line is horizontal or vertical, the slope and
        # negative reciprocal calculations will fail, so do this instead
        if starty==endy or startx==endx:
            if starty == endy:
                y1 = iy + matchDist
                y2 = iy - matchDist
                x1 = ix
                x2 = ix
            if startx == endx:
                y1 = iy
                y2 = iy
                x1 = ix + matchDist
                x2 = ix - matchDist
        else:
            # Get slope of line
            m = float((starty - endy)/(startx - endx))

            # Get negative reciprocal
            negativereciprocal = -1*((startx - endx)/(starty - endy))

            # For all values of slope, calculate perpendicular line
            # with length = matchDist
            if m > 0:
                if m >= 1:
                    y1 = negativereciprocal*(matchDist)+ iy
                    y2 = negativereciprocal*(-matchDist) + iy
                    x1 = ix + matchDist
                    x2 = ix - matchDist
                if m < 1:
                    y1 = iy + matchDist
                    y2 = iy - matchDist
                    x1 = (matchDist/negativereciprocal) + ix
                    x2 = (-matchDist/negativereciprocal)+ ix
            if m < 0:
                if m >= -1:
                    y1 = iy + matchDist
                    y2 = iy - matchDist
                    x1 = (matchDist/negativereciprocal) + ix
                    x2 = (-matchDist/negativereciprocal)+ ix
                if m < -1:
                    y1 = negativereciprocal*(matchDist)+ iy
                    y2 = negativereciprocal*(-matchDist) + iy
                    x1 = ix + matchDist
                    x2 = ix - matchDist
        point1.X = x1
        point1.Y = y1
        point2.X = x2
        point2.Y = y2
        lineArray.add(point1)
        lineArray.add(point2)

        del x1
        del x2
        del y1
        del y2

# Create search cursor in inLine
rows = arcpy.SearchCursor(inLine)

# Get number of records in inLine
numRecords = int(arcpy.GetCount_management(inLine).getOutput(0))

# Create new point files and array to collect values
point1 = arcpy.Point()
point2 = arcpy.Point()
lineArray = arcpy.Array()

# Define counter
counter = 0

# Loop over rows in outLine
for row in rows:
    # Create the geometry object
    feat = row.Shape

    # Get coordinate values as lists
    firstpoint = feat.firstPoint
    lastpoint = feat.lastPoint
    midpoint = feat.centroid

    # Get X and Y values for each point
    startx = firstpoint.X
    starty = firstpoint.Y
    endx = lastpoint.X
    endy = lastpoint.Y
    midx = midpoint.X
    midy = midpoint.Y

    m = ((starty - endy)/(startx - endx+.0001))

    # For all points besides the last one
    if counter < numRecords - 1:
        orientMatchlines(feat,startx,starty)
    # For the last point
    else:
        orientMatchlines(feat,endx,endy)

    #Create insert cursor
    cur = arcpy.InsertCursor(matchlines)

    #Insert new row from array
    feat = cur.newRow()
    #feat.slope = m
    feat.shape = lineArray
    cur.insertRow(feat)
    lineArray.removeAll()

    del cur

    # Increase counter by 1 and start again
    counter = counter + 1

del row
del rows

[GIS] Move points along a line, 100m left or right

This would work better in model builder but you can run it as individual tools.

If you start with Generate Near Table from the points to the line using the options closest and near angle this will give you the angle of the line (radians I think) at the closest location on the line.

Add fields to the near table and original point file NEW_X and NEW_Y and Calculate the new location of these points with trigonometry using cos and sin of the angle and applying it to the points location.

Use Join by attributes to link the FID or OBJECTID (depending on feature type) to the IN_FID on the near table and calculate the NEW_X and NEW_Y with field calculator then export the table using Table Select to clear away the existing geometry and use Feature Class from XY Table if doing manually (right click on table and select create feature class) or if in a model use Make XY Event Layer to generate new points using NEW_X and NEW_Y as the source.

Best Answer

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[GIS] Offsetting points perpendicular to line using ArcMap

[GIS] Move points along a line, 100m left or right

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