Think . . . Spatially - Store & Retrieve Data Anywhere€¦ · Locating Curb Endpoints at...

Think . . . Spatially

Inventorying Linear Assets

From Field to GIS to Database

HILLSBOROUGH COUNTY, FLORIDA

Tampa

NorthNorth

Subdivision DevelopmentThru January 2007

Since 1986, about 30 C-L miles of new roads have been added per yearSince 1986, about 30 C-L miles of new roads have been added per year

A Growing County Lots of Point Assets

• > 96,800 Traffic Signs• > 25,000 Inlets• > 19,000 Sidewalk Ramps• > 17,000 Intersections• Nearly 5,000 Stormwater Manholes• > 1,300 Pedestrian Crossings• > 250 Bridges• > 190 Railroad Crossings

A Growing County Lots L-O-N-G Assets, Too

• > 6,700 Miles of Traffic Lanes• Nearly 4,000 Miles of Pavement Striping• > 3,200 Miles of Shoulders • > 2,600 Miles of Curbs• > 2,200 Miles of Sidewalks• > 170 Miles of Dividers• Nearly 30 Miles of Guard Rails

TOC• Overview• Linear Referencing Concepts• Field Data Collection Protocols and

Software• Route Processing Tools for Post-

processing Field Data• Best-Practices for GPS, Range-finding

and Field Data Collection• The Asset Management System

Overview

• Data Collection Using ArcGIS Engine and ArcPad

• Post Processing Using ArcGIS• Transferring Data to Asset Management

System Using Various Software Tools (Visual Basic)

Ways to Collect Linear Features

• Digitize using high-quality aerial photos• Collect a series of points, or “vertices,”

along the feature• If paralleling other linear features, such as

a street centerline (C-L), then simply collect the start and end points and take advantage of linear referencing

What We Wanted To Do

What Is Linear Referencing?

• Sometimes a picture can save on words

Routes and Linear Referencing

Offset (to right)

-Offset (to left)

FROM

TO

001000

001010

001000

R

R

L

1234

5.00

12345.00

12345.00

12345.00(Sidewalks)

Linear Referencing Concepts

• Takes Advantage of ESRI’s Dynamic Segmentation Support

• Utilizes a Linear Referencing Route System

• Converting Field-collected “Points” to Linear Features

Why Linear Referencing?

• Here’s Another Picture

Real Purty

Speed Limits

Measuring Along Routes

There is only one route (04904.00) nearby and no ambiguity.

There is only one route (04904.00) nearby and no ambiguity.

There are two routes (04899.00 and 04904.00) nearby and two different mileposts. This ambiguity can be resolved by indicating which route ID to use.

There are two routes (04899.00 and 04904.00) nearby and two different mileposts. This ambiguity can be resolved by indicating which route ID to use.

Measuring Along Routes

05827.00

05827.00.316 Mi.

.023 Mi.15.00 Ft

-15.00 Ft

Cherry Rose Cir (05827.00) starts at the intersection with Reflections Blvd. We already know about this ambiguity.

Cherry Rose Cir (05827.00) starts at the intersection with Reflections Blvd. We already know about this ambiguity.

Cherry Rose Cir (05827.00) intersects with itself about 100 feet (.023 Mi.) south of Reflections Blvd.

The route then increases from the intersection in the clock-wise direction all the way around the loop and back to the intersection.

Cherry Rose Cir (05827.00) intersects with itself about 100 feet (.023 Mi.) south of Reflections Blvd.

The route then increases from the intersection in the clock-wise direction all the way around the loop and back to the intersection.

A point at the corner, for a sidewalk end-point, let’s say, introduces a new kind of ambiguity.

The point can be either on the right of the route (15 Ft) at the smaller milepost (.023 Mi.), or on the left (-15 Ft) at the higher milepost (.316 Mi.). Either could be correct.

A point at the corner, for a sidewalk end-point, let’s say, introduces a new kind of ambiguity.

The point can be either on the right of the route (15 Ft) at the smaller milepost (.023 Mi.), or on the left (-15 Ft) at the higher milepost (.316 Mi.). Either could be correct.

Field Data Collection Concept

23

Field Data Collection Software

Street C-LPoints

Manholes

School ZoneStart and End

Field Data Collection Software

Two linear features are already being collected (Curbs and Sidewalks) as indicated by the red boxes around the icons.

Two linear features are already being collected (Curbs and Sidewalks) as indicated by the red boxes around the icons.

Field Data Collection Protocols and Software (Linear Features)

Hillsborough CountyPublic Works Department

Field Data Collection ProtocolsFor

Transportation AssetsJuly 21, 2006

Curb Endpoints

Curb Endpoints

Curb Endpoints

Street Centerline

Stre

et C

ente

rline

Stre

et C

ente

rline

Stre

et C

ente

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Locating Curb Endpointsat Intersections

Use the middle of the Return(the curved corner)

Inte

rsect

ion

Inte

rsect

ion

Inte

rsect

ion

Although a curb usually “drops down” at things like driveways, the curb is considered to be continuous across driveways.Typically, a curb extends for the full length of the block of a street. This is not always the case, but as a rule, curbs will have start and end points at intersections, as in the illustration, above.Another illustration of determining endpoints for curbs is shown for a cul-de-sac, below.

Field Data Collection of Lane CountsLane counts are collected for each side of a street

and includes all lanes from the edge of the road to itscenterline or divider

THRU lanes have end pointsat the center of the intersection(s)they go “thru” or into

TURN lanes have end pointswhere they reach full-width andat the edge of the intersectionthey turn into

Field Data Collection of Pavement MarkingsLong-line Pavement Markings are collected foreach side of a street and includes all markings

from the edge of the road to its centerlineor divider. Centerlines are counted on the first side of the street that is inventoried.

Markings have end pointsat the edge of the intersection(s)they go into

Changes in Markings occurwhere any new line starts ora line ends

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Surface Types

Speed Limit Zones

Sidewalks

Sidewalk Handrails

Shoulders

School Zones

Road Widths

Pavement Markings

One Way

Lane Counts

Guard Rails

Dividers

Curbs

Bike Lanes

Meanwhile, Back in the Office


FROM_MP TO_MP

Voila!!

RefreshGIS View

CloseAccess

PressButton inAccess

Route Processing Steps-Concept

PressToolbarButton

Run RouteLocationWizard

SelectPoints

A custom button to activate Access®

Form w/ button to activate

update query in Access®

Using a Personal GeoDatabase . . .

Route Processing Toolbar

Create Routesfrom C-L GIS

Edit ExistingRoutes+ extend from start+ extend from end+ shorten from start+ shorten from end

Determine Measure (Milepost)and Distance (Offset) for PointData, Like Traffic Signs

Process field-collectedPoint-pairs and Create Linear Events from Them

Add EventsExport to Shape

Route Processing Toolbar

Post Processing Software

Field Data Collection Tools and Best-Practices

• Importance of a Good Centerline• GPS (Global Positioning System)• Laser Range Finding• Database Management

A Good C-L GIS Is Essential


Erroneous C-L Field-corrected C-L

Two pairs of end points with PointPairIDs of

84 – Sidewalk, and87 – Curb

Two pairs of end points with PointPairIDs of

84 – Sidewalk, and87 – Curb

Even though the C-Ls are only 9 feet apart, better placement of it changes the side of the road that the curb and sidewalk are on.

Even though the C-Ls are only 9 feet apart, better placement of it changes the side of the road that the curb and sidewalk are on.


• For this reason, collecting points along centerlines of streets is now part of our field data collection process.

• Points are collected at intersections, geometry changes and at points along curves.

• Back in the office, the C-L geometry is adjusted to “snap” to the field collected points.

GPS Issues

• GPS (Global Positioning System) is neither magic nor fool-proof

• Used carelessly, poor data will result• Know the short-comings and minimize

them as much as possible• Then perform quality control checks on

any data collected using GPS

GPS Issues (cont’d)• Not all GPS equipment are created equal• Satellites are constantly moving and their

“geometry” constantly changing– No two reads at the same location will be

equal– Some conditions better than others, e.g.,

PDOP (Position Dilution of Precision) values• Satellite signals can “bounce” off nearby

objects and cause errors

GPS Best-practices• Cheaper is NOT better• Use equipment/software that can control

quality (and report it)• WAAS (Wide Area Augmentation System)

should not be relied on• Set a PDOP Mask of <= 6 (4 is better)• Average multiple reads, rather than taking

only one read

GPS Best-practices• Portable, or built-in, real-time correction

beacons can sometimes improve quality• Post-processing field data using .ssf files

may improve quality• Use consistent methods in the field• Utilize double-checks in the field and in the

office

Laser Range Finder

A look to the future to improve safety and consistency: PWD is testing LRF technology.

SlopeAngle

Laser Range Finder Terms

Distance

SlopeDistance

STOP

Distance = Sin(Slope Angle) x Slope Distance

Known (X,Y)

Offset (X,Y)

Using the Distance, Azimuth and Known X,Y for the Laser, the Offset X,Y can be determined.

Laser Range Finder Issues

• Magnetic compasses affected by natural and human situations– Earth’s magnetic declination

Why can’t I get my stupid

compass to work?

Laser Range Finder Issues

• Magnetic compasses affected by natural and human situations– Earth’s magnetic declination– Nearby metal (seen or unseen)

• Distance accuracy related to aiming accuracy

• Calibration should be regularly checked and professionally corrected

Laser Range Finder Best-Practices

• Set up the laser on a tripod; hand-held “lazing” should only be used when accuracy is not required

• Make sure the laser is plumb (vertical)• Make sure you can see through the laser’s

sighting device• For long sights, work with the sun behind

you, if possible

Laser Range Finder Best-Practices

• In determining the location of the laser equipment with GPS, use multiple reads

• Use field procedures that either:– Adjust magnetic declination against a known

azimuth, or,– Collect data that can be used to adjust field

data back in the office• Minimize aiming and azimuth errors by

limiting distances “shot” in the field

Relational Database Management System (RDBMS) Fundamentals

• Most asset management systems make use of RDBMSs like Oracle or SQL Server

• Data is in a system of multiple tables that are related by various keys and codes

• This differs from a GIS feature which usually looks like a single table (attributes), unless in a GeoDatabase


GIS Feature

Data

RDBMS Data

User ViewingJoined Data

• Most asset management (AM) systems make use of “business rules” that control how data are coordinated.

• It is possible to join (link) a GIS feature to a table in an RDBMS, as long as both share a common key.

• Transferring data between a GIS feature table and an AM system is limited by the data management tools in the GIS and the AM’s business rules.


GIS Feature

Data

RDBMS Data

User and DataTransfer Tool

• Usually, an intermediate tool (software) is required to transfer data between GIS and RDBMS.

• This tool “knows” how to apply the business rules and how data are mapped between GIS attribute fields and corresponding RDBMS tables and fields.


• Synchronizing a GIS and an RDBMS must be able to handle:– Adding new features– Deleting (expiring) removed features– Modifying existing features

• For purposes of this presentation, GIS data supersedes that in the RDBMS, but that is not always the case


• Most RDBMSs do not have a “spatial” data component, out-of-the-box

• So, what about spatial data?– Usually maintained in the GIS– Recommended exceptions

• Points (store X,Y) in RDBMS, also• Linearly referenced data (store Route ID, From

Milepost, To Milepost) in RDBMS, also


• Why put spatial data in the RDBMS?– Belts and suspenders (redundancy)– Possibility to regenerate GIS data from the

RDBMS, using events• Points regenerate using the (X,Y) values• Linear features regenerate using linear FROM and

TO data– Allows a visual level of QA checking

Recap• Overview• Linear Referencing Concepts• Field Data Collection Protocols and

Software• Route Processing Tools for Post-

processing Field Data• Best-Practices for GPS, Range-finding

and Field Data Collection• The Asset Management System

Questions ?

[email protected](813) 307-1745

Think . . . Spatially - Store & Retrieve Data Anywhere€¦ · Locating Curb Endpoints at...

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