editing how to make your own!. esf laboratory for applied gis 2 manuscript maps paper maps drawn by...

EDITING

How to make your own!

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Manuscript Maps

• Paper maps drawn by a cartographer• Generalization is a problem • Scale is the key to map accuracy

– 1/24,000 scale accuracy is ± ~40’ (.0076 mile)– 1/50,000 scale accuracy is ± ~80’ (.015 mile)– 1/100k scale accuracy is ± ~160’ (.03 mile)– 1/500k scale accuracy is ± ~800’ (.34 mile)– 1/1,000,000 scale is ~ ± 160,000’ (30 miles)

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Accuracy & Generalization

• The generalized stream is not as accurate a representation of the stream as the original

• And if you try to mix data of different scale common lines are NOT going to match

Original

Generalized

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Orthophoto background

Green is County boundary

Yellow is soils layer (NRCS)

This is called the “Coincident Line” problem

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Errors

• From manuscript maps you have data drawn at different scales with different levels of generalization

• From digital data you have differences due to the ways the data was produced and

• they are just different (could be scale)

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So

• Use the metadata to determine, if possible, how the data was created

• and what the scale of the original manuscript map was if it was generated that way

• And what the accuracy of the orthophoto was if the vector data was created by heads up digitizing

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File types

• Shape files• FC• Coverages

– ArcINFO format– PC ArcInfo format

• Rasters of various kinds• TINs (Triangulated Irregular

Networks)• Networks

Can editCan editCannot edit in ArcMap

Can’t even open in ArcMap* nope Yup

Yup

* Open in ArcView 3.3 & save as a shapefile

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Editing Steps

1. Load only the data needed for editing into ArcMap

2. Click on the “Selection” tab at the bottom of the TOC (demo)

3. Make sure only the layer to be edited is selected

4. This gets around the Booby Trap of having the wrong layer in the Target window!

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Set Snapping

• Snapping environment– Select “snapping” from Edit dropdown– Priority of snapping

is the order of thelayers (drag ‘em’).

– In this case the mills will be snapped to the road’s edges.

– Set snapping Tolerance (how close for jump)– Edit/options

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Setting Snapping Stuff

Pixels or map units

No, No, No

Distance between vertices

Number of vertices to be deleted when you

screw up – and you will when using stream

mode!

Tip says what you are snapped to

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Tricks

• Snap poly corner to the corner of another poly…– Move poly’s selection anchor… what?– In edit mode when a poly is selected a “X”

wil appear in the center of the poly– That’s the selection anchor

• Drag it to the corner you want to snap from

• Move the poly towards its new location until it snaps.

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Snapping tricks

• Press “T” will show you what the current snapping tolerance is…

• If you need to change the snapping tolerance often then load the interactive snap tolerance toll to any tool bar– Rt clk blank spot on menu bar, scroll down

to the bottome of the list that appears and click cutomize. Click the Command tab and then Edit and scroll down to the tool

– Drag it to any tool bar (Edit, perhaps)– Clicking on the tool allows you to draw a

circle that is the snapping tolerance you need.

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Sketch Construction Tools: Sketch tool

Use the Sketch tool to create point features and digitize the vertices of line or polygon features. After you finish the sketch, ArcMap adds the finalsegment, and the sketch turns into a feature.

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Sketch Construction Tools: ArcTool

The Arc tool helps you create a segment that isa parametric (true) curve. Instead of being made of numerous vertices, a parametric curve has only two vertices as endpoints.

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Sketch Construction Tools - midpoint

The Midpoint tool lets you define the location of the next vertex by clicking two points; the new vertex is placed at the midpoint of the line between these points.

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Midpoint tool?

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Sketch Construction Tools

The Trace tool helps you create segments that Follow along parallel to an existing segment.

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Trace tool

• Traces along an existing line features (instead of typing the angle and length of each segment.)

• select the parcel features before you can start tracing the road casing feature.

• The Trace tool only follows selected features.

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Autocomplete

• Another very handy trick for creating polygons.– Set the task to autocomplete (under

topology tasks)

#1

#2 #3

Dbl click

These 2vertices put in

automatically

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Streaming

• As you move the cursor along a path vertices are placed at the “stream tolerance” you have specified.

• Good for things like meandering streams

• But is tricky – don’t sneeze!• Turned on and off by right click on the

sketch tool click “streaming” or press F8.

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Split Poly Tool

• Use the “Cut Polygon Features” task• Why

– Makes a perfect match between polys when Split – every time and…

– Select poly to split with the Edit Tool • Use pencil tool to draw a line through

the poly where you want it split• Rt click anywhere to finish the job

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Advanced editing

• This is just the tip of the editing abilities. • The advanced tools let you do things

like…– Extend a line to touch another line– Traverse tool – use COGO data to add to the

edit sketch– Explode tool – Splits a multipart feature into

its component features– Circle tool – draws a circle– Rectangle tool – guess what– Trim tool – trims dangles

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Tricks

• Use arrow keys to pan while editing