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Copyright © 2016 Spatial Analytix, LLC

GIS for Land Surveyors

Precision. Accuracy. Reliability

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GIS as more than just Software

GeoSpatial Data

Geoprocessing

Metadata

AGENDA



How is GIS different than CAD?

Its about Data, not Drawings

Points-Lines-Polygons-Symbology

vs

Topology-Attributes-Analysis



What do these

Colors indicate?

Depth to bedrock

% Sand

Conductivity

% Clay

Hydric Class

Crop Yield



How is GIS different than CAD?

Its about Data, not Drawings

Points-Lines-Polygons-Symbology

vs

Topology-Attributes-Analysis

Raster Data



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GIS data models

Vector model Raster model



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Vector model

Vertices

Polygon

Points

Nodes

Line

X

Y

Features

are stored as a series of x-ycoordinates in a rectangular coordinate system.

Features can have one of three geometry types: points, lines, or polygons.



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GIS data models

Three Pillars of GIS

Imagery (and lots of it)- Raster

Orthos, NAIP, Satellite, UAV

Elevation – Raster and Vector

LiDAR, Contours, DEM, DTM

Vectors- Vector is Vector

Parcels, Planimetrics, NRI



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Storing Elevation Data

Contours

Raster

TIN



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Digital Elevation Model

A DEM has cells or

pixels, each of which

contains a single

elevation.

Regularly spaced array

of elevation values.



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1-15

The raster data model

Rows

ColumnsX, Y location

Raster data fileN rows by M columns

X, Y location

Georeferenced to earth’s surface



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Discrete rasters

Discrete rasters essentially store

features—but in raster format

Have relatively few values that

change abruptly from one category

to another

roads

land use



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Continuous rasters

Continuous rasters store surfaces or fields of variables that change continuously over space

Many potential values. Adjacent cells rarely share the same value.

Air photo

DEM



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Continuous data

Raster is the best way to store continuously

changing values such as elevation or distance

Analysis faster and more flexible than vectors

for many applications

Vertices slow processing down with vectors

Some analysis only possible using rasters



The Power of Rasters: Map Algebra

Rasters are essentially arrays of

numbers

Can be added, subtracted, etc

Line up matching cells vertically

Copyright © 2015 by Maribeth H. Price11-19

5 7

2 4

3 2

1 6

8 9

3 10

Ingrid1

+

Ingrid2

=

Outgrid

Map algebra



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Raster analysis functions

Density

Least cost path

Distance Interpolation

Viewshed

Buffers



GIS Software

Free- QGIS

Affordable- Global Mapper

Industry Standard- ArcGIS

Specialty Extensions…



ArcGIS Options



GIS DATA TYPES

Imagery

NYS Orthos, local orthos

Hydrography

Stream lines

Water body polygons

Wetlands (NWI)

Planimetrics

Building footprints

Pavement/sidewalks

Land cover

Impervious Surface



GIS DATA TYPES

Elevation Data

Contours

DEMs

LiDAR Point Clouds

Parcel Data

Boundaries

Centroids

RPS Data Extract (lots of Attribute data)

Local Data

Zoning

NRI



Where do I get data?



NYS DATA RESOURCES

NYS GIS Clearinghouse

https://gis.ny.gov/

NYS DEC

http:// www.dec.ny.gov/eafmapper/

http:// www.dec.ny.gov/gis/erm/

NYS DOS- Geographic Information Gateway

http://opdgig.dos.ny.gov/

Counties/municipalities

Westchester, Monroe, Dutchess, Albany, Erie, etc…


https://gis.ny.gov/

http://opdgig.dos.ny.gov/


REGIONAL DATA RESOURCES

PA MAP = PASDA

http://www.pasda.psu.edu/

NJ Bureau of GIS

http://www.nj.gov/dep/gis/listall.html

MA Office of Geographic Information

ugly

CT DEEP or UCONN MAGIC

www.ct.gov/deep/gisdata

http://magic.lib.uconn.edu/connecticut_data.html


http://www.pasda.psu.edu/

http://www.nj.gov/dep/gis/listall.html

http://www.ct.gov/deep/gisdata

http://magic.lib.uconn.edu/connecticut_data.html


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GIS Data Compilation

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Old: All data is local and

works in the GIS program



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Web Mapping Services

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New: Servers provide data and services to many uses

on many platforms



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Types of services Map services and base maps

Provides maps as static images

Pre-symbolized; attributes not accessible

Feature service

Provides GIS features and attributes

Image service

Provides seamless access to large image datasets from satellites or aerial photography

Geoprocessing service

A tool or analysis that runs on the server and passes the result down to the user

Layer package

A single layer or group layer downloaded to local computer for use in ArcGIS Desktop

Map package

An entire map with many layers downloaded to local computer

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Applications vs Geoprocessing

Geoprocessing = Tools. Processes that run and give you a result

Line of sight, Slope, flow direction

Buffer, Intersect, Clip, Merge

Applications = What you do with those Tools

Risk Assessment

Site Selection

Multi-Criteria Analyses

Scenario development

Apps- coded interfaces that do specific things

Web apps

Desktop apps

GEOPROCESSING



Dissolving

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Maribeth

H. Price

10-44

Dissolve polygons on habitat or soil class

GEOPROCESSING



Buffering

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Constructs polygon areas within a specified distance of features.

Single buffers around linesMultiple buffers around points

GEOPROCESSING



Overlay Point-in-polygon overlay

Line-in-polygon overlay

Polygon-on-polygon overlay

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GEOPROCESSING



Habitat analysis with Intersect

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1. Use queries to isolate features of interest from input layers.

2. Intersect selection layers to find common areas.

GEOPROCESSING



Hazards mapping with Intersect

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Residential areas Opeche formation Areas of both

GEOPROCESSING



Map Algebra

Rasters are essentially arrays of

numbers

Can be added, subtracted, etc

Line up matching cells vertically

Copyright

© 2015

by

Maribeth

H. Price

11-49

5 7

2 4

3 2

1 6

8 9

3 10

Ingrid1

+

Ingrid2

=

Outgrid

Map algebra



Map Algebra: Conversions

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[Precip_cm] / 2.54

Precip in cm Precip in inches



Map Algebra: Cut and fill

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H. Price

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[Initial surface] – [final surface]

Cut

Fill



Map Algebra: model

equations

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Complex expressions with multiple inputs to calcuaterisk or hazard index.

Estimated Runoff is Calcuated based on four input grids: precip, slope, soil infiltration, and vegetation cover.

[Precip] * 2 + [Slope] * 4 / ( [Erode] – [Vegcover]



Map Algebra: logical operators

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11-53[Elevation] > 1200

Logical operators produce either TRUE (1) or FALSE (0) values in the output grid, based on whether a cell meets the condition.

[Slope] < 10 [crowncov] < 70 AND [crowncov] > 40



Boolean rasters Boolean rasters represent maps of True/False states for a particular

condition

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11-54Slope < 10 degrees?

1 = True

0 = False



Boolean overlay (AND)

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0

1

0

1

0

1

AND =

[PrecipGT60] AND [ElevGT1500]

Precip > 60 cm Elevation > 1500 m Lodgepole Pine

Reforestation

habitat



AND is also multiplication

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Maribeth

H. Price

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0

1

0

1

0

1

x =

Boolean AND is equivalent to multiplication. So multiplying layers works just as well.

1 AND 1 = 1

1 AND 0 = 0

0 AND 1 = 0

0 AND 0 = 0

1 × 1 = 1

1 × 0 = 0

0 × 1 = 0

0 × 0 = 0

Precip > 60 cm Elevation > 1500 m Lodgepole habitat



Additive Boolean overlay

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11-57

0

1

2

0

1

0

1

+ =

ADD the layers together to create a ranked result.

Precip > 60 cm Elevation > 1500 m Lodgepole habitat



QUIZ What are the 3 Pillars of a GIS?

Imagery, Elevation, Vectors



QUIZ What are the 3 Pillars of a GIS?

Imagery, Elevation, Vectors

What are the two fundamental dataypes of a GIS?

Raster and Vector

Name 3 different ways to represent elevation data

Points, TIN, Raster (DEM), Vector (Contours)

Give 3 examples of point data you might need to display as a continuous surface

Elevation, well data, air quality, precipitation, noise



Landfill Site Selection

Problem: Find potential locations for a new landfill using these criteria

On flat terrain <= 10 degrees slope

No more than 1 km from an existing road

At least 500 meters from a stream

Meadow or low-density forest

Private Property

Minimum Parcel 10 acres

Zoned Commercial/Industrial

Develop a Boolean raster for each condition with 1 = desirable area, 0 =

not desirable areaCopyright

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Maribeth

H. Price

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Slope condition

1. Use slope function on elevation raster.

2. Use map algebra logical operator to produce Boolean map of slope <= 10 degrees.



Road distance condition

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1. Use distance function to create raster of distance from roads.

2. Use logical operator in map algebra to create Boolean raster of areas within 1000 meters of a road.

[Distance] <= 1000



Stream distance condition

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Maribeth

H. Price

11-64

1. Use distance function to create raster of distance from streams.

2. Use a logical operator in map algebra to create a Boolean map of areas more than 500 meters from a stream.

[Distance] > 500



Vegetation condition

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1. Select suitable vegetation density and create a layer from the selected polygons.

2. Convert the selected vegetation layer to a raster using the density attribute.

3. Reclassify the three density values all to 1 and the NoData areas to 0.



Find areas with Boolean AND

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[Slope] AND [Roads] AND [Streams] AND [Vegetation]



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Metadata

• Contains information about data that people need to understand the data and evaluate its quality• Should be provided with every data set distributed to the public• Advised for in-house data as well



GIS for Land Surveyors

Precision. Accuracy. Reliability


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