From ALI to Mapped ALI

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From ALI to Mapped ALI

• How 9-1-1 Calls
• Are Mapped at the PSAP
• Presented by Susan Cunningham
• Spatial Data Research, Inc.
• December 30, 2008

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The Basics

• The location information from the data portion of
  a 9-1-1 call is read by the mapping software and
  the location of the telephone that made the 9-1-1
  call is interpreted on the map at the PSAP.

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Step 1

• The components of the ALI that describe the
  callers location are extracted or read from the
  ALI data by the mapping software.
• The mapping software might get the information
  from a log file or directly from the ALI itself
  via a serial, network or other comm connection.

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Step 1 cont.

• The mapping software reads the appropriate
  information based on the ALI format used at that
  PSAP. This ALI schematic shows the row and
  column position for every piece of data in the
  ALI stream.
• In New Mexico, the 30W format is the standard.

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Step 1 cont.
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Step 1 cont.

• In the chart on the previous slide, the house
  number is located in row 4, columns 1-10. The
  mapping software will look for and read the house
  number only from these specific positions and
  assumes that all data in these positions describe
  the house number. If data is sent that does not
  adhere to the 30W format, mapping the call may
  fail.

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Step 2

• The mapping software attempts to match the road
  name from the ALI to a road name in the GIS road
  centerline data.
• The mapping software creates a road name index
  whenever the software is launched. Re-indexing
  each time the software is launched assures an
  accurate index of road names when new data is
  loaded.

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Step 2 cont.

• Location from ALI
• 250 Cabresto Rd Comm Questa
• First Match Road Name Cabresto Rd

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Step 2 cont.
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Step 2 cont.

• Location from ALI
• 250 Cabresto Rd Comm Questa
• Second Find segment that contains 250

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Step 2 cont.
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Step 3

• Location from ALI
• 250 Cabresto Rd Comm Questa
• Third Pro-rate distance along chosen road
  segment to locate position of 250

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Step 3 cont.

• Range on selected road segment is 136-260.
• 260-136 94 250-136 84 84/94
  89
• Address 250 is located 89 of way from
  beginning of road segment to end on even side
  of road.

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Step 3 cont.
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Duplicates

• Many PSAPs must work with duplicate road names.
  Large, consolidated PSAPs receive calls from a
  wide geographic area, often from several
  communities that may have non-unique road names.
  For example.
• 9-1-1 call from 7 Montoya Rd

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Duplicates

• 9-1-1 call from 7 Montoya Rd
• First Find Montoya Rd in GIS Road Data

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Duplicates

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Duplicates

• 9-1-1 call from 7 Montoya Rd
• Next Find the segment that contains the
  address 7

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Duplicates

Three potential matches Three different locations
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Duplicates

• 9-1-1 call from 7 Montoya Rd COMM
  Penasco
• If the GIS data contains COMMUNITY information,
  the call can be mapped by matching the MSAG
  Community in the ALI string with the MSAG
  Community designation in the GIS Data.

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Duplicates

Only one match when community is used along with
the road name and address range.
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Accurate 9-1-1 Call Mapping

• REQUIRES
• Good addressing based on accurate intervals.

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Accurate 9-1-1 Call Mapping

• INTERVAL ADDRESSING Addresses increase by a
  known, constant interval based on distance.
• In areas where SDR works, much of the rural
  addressing is based on 100 or 1000 addresses per
  mile of roadway.
• 250 Cabresto Rd would be located 2.5 miles from
  the beginning of Cabresto Rd.

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Accurate 9-1-1 Call Mapping

• IRREGULAR ADDRESSING If an address does not
  follow the addressing interval, it will not map
  correctly at PSAPs using road centerlines for
  9-1-1 call location.

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Accurate 9-1-1 Call Mapping

• Numbers represent actual location of homes. Red
  arrow shows where 249 mapped in the PSAPs call
  mapping software.

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Accurate 9-1-1 Call Mapping

• Why this happenedhow to fix it.

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Accurate 9-1-1 Call Mapping

• If the high/low range on a road segment does not
  represent the true potential range of addresses
  on a road, the 9-1-1 call will not map correctly.

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Accurate 9-1-1 Call Mapping

• 46 Buck Rd maps incorrectly as range on road is
  incorrect.

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Accurate 9-1-1 Call Mapping

• 46 Buck Rd maps incorrectly as range on road is
  incorrect. Mapping can be corrected by changing
  the left to range to 46 and the right to
  range to 47.

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Actual vs Potential Block Ranges

• City/Town blocks usually increment by 100.
  However, the actual addressing on a typical block
  might be 100-114 (for example) and not really
  100-199.

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Actual vs Potential Block Ranges

• 816 E Ellis Ave where range is 800-818

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Actual vs Potential Block Ranges

• 816 E Ellis Ave where range is 800-899

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Summary

• Location data is transmitted to the PSAP with a
  landline calls ALI
• Call Mapping software extracts the location data
  and attempts to plot it on the map
• House number, road name, road range and community
  data are required for optimal mapping
• Address datamaintained at the local telephone
  company database levelmust match mapping data
  for accurate mapping