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Boundary Survey / Pin Survey: A Survey of a parcel of land recorded at
the County Clerk and Recorders Office. The survey drawing provides the
property legal description, information on the lot lines and lot corners, any
easements or encroachments (buildings, fences, driveways, etc.). All corners
of the lot must be found or set and shown on the drawing. Cost $600 & up
the County Clerk and Recorders Office. The survey drawing provides the
property legal description, information on the lot lines and lot corners, any
easements or encroachments (buildings, fences, driveways, etc.). All corners
of the lot must be found or set and shown on the drawing. Cost $600 & up
You can request
additional surveying
items to be included
on your survey, such
as: flood elevations,
contours, adjacent
buildings, bulk plain
information, trees etc.
additional surveying
items to be included
on your survey, such
as: flood elevations,
contours, adjacent
buildings, bulk plain
information, trees etc.
Boundary Improvement Survey: This is a Boundary Survey. The
survey drawing provides the boundary survey information and
accurately depicts all buildings, concrete, fences, driveways and
above ground utilities. Cost $650 & up
survey drawing provides the boundary survey information and
accurately depicts all buildings, concrete, fences, driveways and
above ground utilities. Cost $650 & up
ALTA/ACSM surveys: The most expensive and detailed surveys
similar to a Boundary Improvement Survey with optional details. The
optional item list can be found at acsm.net. Ordered for commercial
properties only 99.9% of the time. If you have a residential property
you do not need a ALTA/ACSM survey in most cases.
similar to a Boundary Improvement Survey with optional details. The
optional item list can be found at acsm.net. Ordered for commercial
properties only 99.9% of the time. If you have a residential property
you do not need a ALTA/ACSM survey in most cases.
To find your legal description or how old your neighborhood is look at the
Assessor's link for your county on the Home Page.
Assessor's link for your county on the Home Page.
Notes prepared for the LORMAN ALTA /ACSM seminar
Topographic Survey And Engineering Design Survey
- When Is A Full Topographic Survey Required?
Engineers and Architects typically require elevation information to reference design
height criteria, roadway design, flood control, water quality designs and many other
engineering tasks. Typically ALTA/ACSM surveys do not have elevation data other than
building heights. Engineers ordering ALTA surveys with elevations should make sure the
surveyor has a good idea of what the survey is intended to be used for.
ALTA/ACSM land title surveys should include a flood elevation certification stating
the relationship to any FEMA flood hazard area and the map and panel data used for this
determination. In some cases the surveyor may need to survey the topography of the site
to correctly determine flood hazard limits. Areas that have had fill placed on them
without a permit are often required to be surveyed at the cost of the contractor who
placed the fill.
Elevation Certificates & MT1 forms for LOMA’s and insurance are not full
topographic surveys. Elevation information is given on the certificate including the
building floor, basement floor, garage floor, machinery servicing the building and
adjacent grades to the structure. The MT1 form and MT-EZ form are for vacant
properties and only the lowest lot elevation is given.
Positional Accuracy And Mapping Standards
Allowable Relative Positional Accuracy For Measurements Controlling Land Boundaries On ALTA/ACSM
Land Title Surveys
-
The allowable accuracy set by the American Congress on Surveying & Mapping
between any 2 points on an ALTA/ACSM survey is 0.07’ + 50ppm.
Modern surveying equipment can produce results in this range only if proper setup
and calibrations are made. This requires experienced field personnel and periodic
servicing of the equipment. Understanding the measurement techniques and adjustments
needed of each instrument used in the field is necessary. For instance temperature and
altitude must be correctly input into the EDM to make the proper adjustments to the
returned values. Different manufacturers of survey instruments require separate
knowledge of each instrument. A Topcon or Pentax instrument measures from the center
of the mount while a Leica instrument measures 34mm offset from the center of the
mount. This requires the instrument person to use the correct prism offset in the data
collector.
- U.S. National Map Accuracy Standards
USGS National Map Accuracy Standards are:
• 90% of the horizontal points on the map are within +/- 40 feet of their actual position on Earth in the
horizontal direction.
This horizontal direction refers to 7.5 minute Quad maps produced by the USGS not survey quality maps.
• 90% of the vertical elevations are within +/- ½ of the contour interval for the map.
This is the standard used for the 7.5 minute Quad. Maps and most topographic surveys.
This means a 1 foot contour map must have 90% of the contours within ½ foot, a 10 foot
contour map must have 90% of all contours within 5 feet.
(Questions)
- Geospatial Positioning Accuracy Standards, Standards For Geodetic Networks
Standards set by the National Spatial Reference System (NSRS)
Geodetic Control Stations:
1. Must be physical marked points and they must be recoverable.
2. The accuracy of the coordinates must be stated and should be at the 95%
confidence level.(least squared value) The accuracy of the coordinates is a required
data element.
3. The reference datum for the coordinates must be stated.
4. The coordinates must be derived through a connection to NSRS.
Surveying Accuracy – Traditional Methods
Using a transit and chain was the traditional method of surveying until the EDM was
developed in the 1970’s. Angles were hand written in field books and distances were
chained using a surveyors chain (66ft). 80 chains = 1 mile. Corrections for slope,
temperature and chain sag were made to field measurements and accuracy was at times
very good other times not so good. As you could expect large errors exist in some older
recorded deeds and documents.
- Surveying Accuracy – Total Station – EDM Technology
The EDM (electronic distances meter) was first developed by wild in 1969. By the late
1980’s most surveyors had Only used one. Early EDM models were slow and the setup
required the transit to be removed from the tripod.
The “Top Mount EDM” this instrument was fixed on top of the transit and could be
used much easier than the older models. Still the top mount had limitations. The EDM
read the slope distance not a horizontal distance. The vertical angle was read by the
transit operator had to be written down or input into a calculator or the EDM to compute
a horizontal distance.
In 1977 the Total Station was developed integrating a transit, EDM and data collection
capabilities. The modern Total Station specifications for survey instruments are around 2-
3mm + 3ppm.
- Surveying Accuracy – GPS Technology
GPS technology was introduced to the surveying profession in the late 80’s
GPS observations required long occupation times up to 2 hours. In the early 90’s Fast
Static techniques were developed and the observation times required began to drop.
Today post processed Static GPS accuracy ranges form 2mm -5mm. This requires
observations for periods about 12 minutes + 2 minutes per baseline Kilometer.
Other conditions like sky view obstructions and satellite availability also must be taken
into consideration prior to assuming this time guideline is sufficient.
RTK (real time kinematic) survey GPS receivers give real time survey grade positions
Almost instantly without post processing of the GPS carrier phase data RTK
surveys have accuracies at 10mm - 20mm.
- Listing Results On Survey Maps
If an ALTA/ACSM Land Title Survey does not meet the 0.07 feet + 50ppm
ALTA/ACSM standard the certification must state what the positional tolerance is.
The tolerance is stated in feet on the certification.
On other types of surveys tolerance may be stated as +/- and “More or Less
Dimensions. This is typically not done except on older surveys
of steep mountain properties and (ILC’s)
- How Are Property Limits (Land Boundaries) Established?
A field visit to a boundary survey site typically begins with a search for the corners of
the immediate property. The surveyor must measure and evaluate the found corners
accuracies in comparison to the recorded plat map or legal description. Adjacent lots
should then be examined to conform to recorded documents. From this comparison the
surveyor must decide if the found corners meet the survey accuracy desired and are in the
true position described in the legal description and documents provided.
In most instances all the corners are not found, and the surveyor must expand the
survey to adjacent lots and platted block corners. Even still the surveyor may find nothing
or find conflicting monuments in the block. The survey must then again be expanded to
the Public Land System or other local range lines. If the survey is tied to the Public Land
System it should be enough, however some cases with old legal descriptions or plats
these quarter section ties contain large errors due to the measurement techniques used at
the time. In these cases fences and street improvements may be the best evidence to establish
the correct lines.
- How Are Specifications For Topographic Information Established?
Engineers have different requirements however most of the time they want the highest
accuracy available. Typically this is 1 foot contours and spot elevations.
Spot elevations are not part of the standard ALTA/ACSM survey optional items.
Often the surveyor is ask to add topographic information to the ALTA/ACSM survey by
the engineer later in the design process.
The local Planning and Zoning administrators and community flood managers should
provide the datum and benchmark information prior to the topographic survey. This will
help the design and planning process go smoothly.
Use Of GPS To Complete Surveys
GPS is used for many surveying applications. If used correctly GPS can greatly
increase productivity and accuracy for large surveys. Limitations exist in all types of
surveying equipment so the surveyor must be able to evaluate each project to determine if
GPS will be an asset or not. If the survey to be completed is a large parcel, in
mountainous terrain or requires a quarter section breakdown, GPS is likely to provide the
surveyor with data in a few hours that could have taken days with a Total Station.
A GPS receiver will not work in the trees, under bridges close to buildings and only
meets accuracy specifications in ideal conditions. A surveyor should be familiar with
these limitations. Some projects require GPS positions regardless of the conditions. For
these the surveyor must combine other measurement techniques to the GPS data to get
accurate positions of survey points. For instance: a survey control point is located under a
tree. The GPS receiver will not keep a fix on the satellites above if the surveyor sets the
GPS antenna directly on the point under the tree. This is called “loss of lock” uncorrected
and inaccurate data is all that is available to the surveyor. The surveyor can set GPS
points outside of the trees obstruction and the use more conventional methods to survey
into the point under the tree. If a horizontal position is the only requirement the surveyor
may simply chain from two known GPS points to the point under the tree.
Control surveys made using Static GPS techniques are the most reliable. Using these
in any large control network project will increase the accuracy.
Construction surveys can often benefit from the use of GPS. RTK stakeout
capabilities have made construction staking much faster and easier on the surveyor. Often
construction sites are free of large overhead obstructions and GPS equipment performs
very well. Most sites have several line of site problems such as earth moving equipment,
trucks and trailers. The Total Station is limited to line of site surveying and these become
difficult to work around.
- Establishing Datum
Vertical Datum:
A local datum, assumed datum, NGVD 1929 or NAVD1988
Can be used in topographic mapping, the question of what datum should be used is an
important first step to a topographic survey. The local Planning and Zoning department
should be able to give you datum information along with some direction to local
benchmarks. The most commonly used vertical datum in the past was NGVD 1929. In
the last few years most local governments have converted to the NAVD 1988 datum.
NGS (National Geodetic Survey) no longer publishes the 1929 datum so to use or
reference it surveyors must find old benchmarks or use NGS software to convert the
datum from NAVD 1988 to NGVD 1929. Still some local flood communities still have
there own datum not related to the NGS datum.
Today GPS users can use NGS tools such as C.O.R.S. (Continuously Operating
Reference Stations and OPUS (Online Positioning User Service) to reference NGS data
and State Plane coordinate values.
Horizontal Datum:
Many horizontal datum systems exist. The NGS publishes geodetic and state
plane coordinates in NAD 1983 (North American Datum of 1983) these are useful
to local governments and utility companies for large scale mapping. They are not
used very often in property surveys or ALTA/ACSM Land Title Surveys.
For these a local ground coordinate system is established by the surveyor. Without a
ground system the surveyor’s measurements would not relate to ground distances as
deeds and plats do. For GPS user’s geodetic coordinates can be converted into a ground
system using software and the maps are drafted from the ground data.
- Aerial Topographic Surveys
Aerial Topography is currently the best method to survey very large parcels and areas
not easily accessible. The aerial survey accuracies usually exceed mapping standards.
One foot contours are possible however ground surveys will provide higher accuracies.
The land surveyor’s role in Aerial Surveys typically is to establish a control panel
network. Panels are marked with a large white “Y” having 3-6 foot long and 1 foot wide
legs. The control panels are accurately surveyed usually to ALTA/ACSM standards and
tied to local control and or quarter section lines. The panels are then used to scale the
aerial photograph data.
Another role may be to survey areas under canopy or underwater where the aerial data
is missing information. This is may be time consuming and costly because the
surveying instruments also have trouble in these conditions. A GPS receiver will not
produce accurate results as discussed earlier, and Total Stations have line of site problems
with trees and foliage.
Positional Accuracy And Mapping Standards
&
Topographic Survey And Engineering Design Survey
Prepared for Lorman Educational Services
By: Curtis E. Carroll, PLS
Bear Creek Land Surveying
8801 West Jewell Place
Lakewood, CO 80227
www.bearcreeklandsurveying.com
Topographic Survey And Engineering Design Survey
- When Is A Full Topographic Survey Required?
Engineers and Architects typically require elevation information to reference design
height criteria, roadway design, flood control, water quality designs and many other
engineering tasks. Typically ALTA/ACSM surveys do not have elevation data other than
building heights. Engineers ordering ALTA surveys with elevations should make sure the
surveyor has a good idea of what the survey is intended to be used for.
ALTA/ACSM land title surveys should include a flood elevation certification stating
the relationship to any FEMA flood hazard area and the map and panel data used for this
determination. In some cases the surveyor may need to survey the topography of the site
to correctly determine flood hazard limits. Areas that have had fill placed on them
without a permit are often required to be surveyed at the cost of the contractor who
placed the fill.
Elevation Certificates & MT1 forms for LOMA’s and insurance are not full
topographic surveys. Elevation information is given on the certificate including the
building floor, basement floor, garage floor, machinery servicing the building and
adjacent grades to the structure. The MT1 form and MT-EZ form are for vacant
properties and only the lowest lot elevation is given.
Positional Accuracy And Mapping Standards
Allowable Relative Positional Accuracy For Measurements Controlling Land Boundaries On ALTA/ACSM
Land Title Surveys
-
The allowable accuracy set by the American Congress on Surveying & Mapping
between any 2 points on an ALTA/ACSM survey is 0.07’ + 50ppm.
Modern surveying equipment can produce results in this range only if proper setup
and calibrations are made. This requires experienced field personnel and periodic
servicing of the equipment. Understanding the measurement techniques and adjustments
needed of each instrument used in the field is necessary. For instance temperature and
altitude must be correctly input into the EDM to make the proper adjustments to the
returned values. Different manufacturers of survey instruments require separate
knowledge of each instrument. A Topcon or Pentax instrument measures from the center
of the mount while a Leica instrument measures 34mm offset from the center of the
mount. This requires the instrument person to use the correct prism offset in the data
collector.
- U.S. National Map Accuracy Standards
USGS National Map Accuracy Standards are:
• 90% of the horizontal points on the map are within +/- 40 feet of their actual position on Earth in the
horizontal direction.
This horizontal direction refers to 7.5 minute Quad maps produced by the USGS not survey quality maps.
• 90% of the vertical elevations are within +/- ½ of the contour interval for the map.
This is the standard used for the 7.5 minute Quad. Maps and most topographic surveys.
This means a 1 foot contour map must have 90% of the contours within ½ foot, a 10 foot
contour map must have 90% of all contours within 5 feet.
(Questions)
- Geospatial Positioning Accuracy Standards, Standards For Geodetic Networks
Standards set by the National Spatial Reference System (NSRS)
Geodetic Control Stations:
1. Must be physical marked points and they must be recoverable.
2. The accuracy of the coordinates must be stated and should be at the 95%
confidence level.(least squared value) The accuracy of the coordinates is a required
data element.
3. The reference datum for the coordinates must be stated.
4. The coordinates must be derived through a connection to NSRS.
Surveying Accuracy – Traditional Methods
Using a transit and chain was the traditional method of surveying until the EDM was
developed in the 1970’s. Angles were hand written in field books and distances were
chained using a surveyors chain (66ft). 80 chains = 1 mile. Corrections for slope,
temperature and chain sag were made to field measurements and accuracy was at times
very good other times not so good. As you could expect large errors exist in some older
recorded deeds and documents.
- Surveying Accuracy – Total Station – EDM Technology
The EDM (electronic distances meter) was first developed by wild in 1969. By the late
1980’s most surveyors had Only used one. Early EDM models were slow and the setup
required the transit to be removed from the tripod.
The “Top Mount EDM” this instrument was fixed on top of the transit and could be
used much easier than the older models. Still the top mount had limitations. The EDM
read the slope distance not a horizontal distance. The vertical angle was read by the
transit operator had to be written down or input into a calculator or the EDM to compute
a horizontal distance.
In 1977 the Total Station was developed integrating a transit, EDM and data collection
capabilities. The modern Total Station specifications for survey instruments are around 2-
3mm + 3ppm.
- Surveying Accuracy – GPS Technology
GPS technology was introduced to the surveying profession in the late 80’s
GPS observations required long occupation times up to 2 hours. In the early 90’s Fast
Static techniques were developed and the observation times required began to drop.
Today post processed Static GPS accuracy ranges form 2mm -5mm. This requires
observations for periods about 12 minutes + 2 minutes per baseline Kilometer.
Other conditions like sky view obstructions and satellite availability also must be taken
into consideration prior to assuming this time guideline is sufficient.
RTK (real time kinematic) survey GPS receivers give real time survey grade positions
Almost instantly without post processing of the GPS carrier phase data RTK
surveys have accuracies at 10mm - 20mm.
- Listing Results On Survey Maps
If an ALTA/ACSM Land Title Survey does not meet the 0.07 feet + 50ppm
ALTA/ACSM standard the certification must state what the positional tolerance is.
The tolerance is stated in feet on the certification.
On other types of surveys tolerance may be stated as +/- and “More or Less
Dimensions. This is typically not done except on older surveys
of steep mountain properties and (ILC’s)
- How Are Property Limits (Land Boundaries) Established?
A field visit to a boundary survey site typically begins with a search for the corners of
the immediate property. The surveyor must measure and evaluate the found corners
accuracies in comparison to the recorded plat map or legal description. Adjacent lots
should then be examined to conform to recorded documents. From this comparison the
surveyor must decide if the found corners meet the survey accuracy desired and are in the
true position described in the legal description and documents provided.
In most instances all the corners are not found, and the surveyor must expand the
survey to adjacent lots and platted block corners. Even still the surveyor may find nothing
or find conflicting monuments in the block. The survey must then again be expanded to
the Public Land System or other local range lines. If the survey is tied to the Public Land
System it should be enough, however some cases with old legal descriptions or plats
these quarter section ties contain large errors due to the measurement techniques used at
the time. In these cases fences and street improvements may be the best evidence to establish
the correct lines.
- How Are Specifications For Topographic Information Established?
Engineers have different requirements however most of the time they want the highest
accuracy available. Typically this is 1 foot contours and spot elevations.
Spot elevations are not part of the standard ALTA/ACSM survey optional items.
Often the surveyor is ask to add topographic information to the ALTA/ACSM survey by
the engineer later in the design process.
The local Planning and Zoning administrators and community flood managers should
provide the datum and benchmark information prior to the topographic survey. This will
help the design and planning process go smoothly.
Use Of GPS To Complete Surveys
GPS is used for many surveying applications. If used correctly GPS can greatly
increase productivity and accuracy for large surveys. Limitations exist in all types of
surveying equipment so the surveyor must be able to evaluate each project to determine if
GPS will be an asset or not. If the survey to be completed is a large parcel, in
mountainous terrain or requires a quarter section breakdown, GPS is likely to provide the
surveyor with data in a few hours that could have taken days with a Total Station.
A GPS receiver will not work in the trees, under bridges close to buildings and only
meets accuracy specifications in ideal conditions. A surveyor should be familiar with
these limitations. Some projects require GPS positions regardless of the conditions. For
these the surveyor must combine other measurement techniques to the GPS data to get
accurate positions of survey points. For instance: a survey control point is located under a
tree. The GPS receiver will not keep a fix on the satellites above if the surveyor sets the
GPS antenna directly on the point under the tree. This is called “loss of lock” uncorrected
and inaccurate data is all that is available to the surveyor. The surveyor can set GPS
points outside of the trees obstruction and the use more conventional methods to survey
into the point under the tree. If a horizontal position is the only requirement the surveyor
may simply chain from two known GPS points to the point under the tree.
Control surveys made using Static GPS techniques are the most reliable. Using these
in any large control network project will increase the accuracy.
Construction surveys can often benefit from the use of GPS. RTK stakeout
capabilities have made construction staking much faster and easier on the surveyor. Often
construction sites are free of large overhead obstructions and GPS equipment performs
very well. Most sites have several line of site problems such as earth moving equipment,
trucks and trailers. The Total Station is limited to line of site surveying and these become
difficult to work around.
- Establishing Datum
Vertical Datum:
A local datum, assumed datum, NGVD 1929 or NAVD1988
Can be used in topographic mapping, the question of what datum should be used is an
important first step to a topographic survey. The local Planning and Zoning department
should be able to give you datum information along with some direction to local
benchmarks. The most commonly used vertical datum in the past was NGVD 1929. In
the last few years most local governments have converted to the NAVD 1988 datum.
NGS (National Geodetic Survey) no longer publishes the 1929 datum so to use or
reference it surveyors must find old benchmarks or use NGS software to convert the
datum from NAVD 1988 to NGVD 1929. Still some local flood communities still have
there own datum not related to the NGS datum.
Today GPS users can use NGS tools such as C.O.R.S. (Continuously Operating
Reference Stations and OPUS (Online Positioning User Service) to reference NGS data
and State Plane coordinate values.
Horizontal Datum:
Many horizontal datum systems exist. The NGS publishes geodetic and state
plane coordinates in NAD 1983 (North American Datum of 1983) these are useful
to local governments and utility companies for large scale mapping. They are not
used very often in property surveys or ALTA/ACSM Land Title Surveys.
For these a local ground coordinate system is established by the surveyor. Without a
ground system the surveyor’s measurements would not relate to ground distances as
deeds and plats do. For GPS user’s geodetic coordinates can be converted into a ground
system using software and the maps are drafted from the ground data.
- Aerial Topographic Surveys
Aerial Topography is currently the best method to survey very large parcels and areas
not easily accessible. The aerial survey accuracies usually exceed mapping standards.
One foot contours are possible however ground surveys will provide higher accuracies.
The land surveyor’s role in Aerial Surveys typically is to establish a control panel
network. Panels are marked with a large white “Y” having 3-6 foot long and 1 foot wide
legs. The control panels are accurately surveyed usually to ALTA/ACSM standards and
tied to local control and or quarter section lines. The panels are then used to scale the
aerial photograph data.
Another role may be to survey areas under canopy or underwater where the aerial data
is missing information. This is may be time consuming and costly because the
surveying instruments also have trouble in these conditions. A GPS receiver will not
produce accurate results as discussed earlier, and Total Stations have line of site problems
with trees and foliage.
Positional Accuracy And Mapping Standards
&
Topographic Survey And Engineering Design Survey
Prepared for Lorman Educational Services
By: Curtis E. Carroll, PLS
Bear Creek Land Surveying
8801 West Jewell Place
Lakewood, CO 80227
www.bearcreeklandsurveying.com
BEAR CREEK LAND SURVEYING
Building a new garage: within 3
feet of your property you will need a
Boundary Improvement Survey
Building a fence: You may need a
Boundary Survey
Building a house: You will need a
Boundary Survey with the adjacent
houses located and elevations at the
corners and mid points of your lot
lines
Adding on to your house: You will
need a Boundary Improvement
Survey with the adjacent houses
located and elevations at the corners
and mid points of your lot lines
feet of your property you will need a
Boundary Improvement Survey
Building a fence: You may need a
Boundary Survey
Building a house: You will need a
Boundary Survey with the adjacent
houses located and elevations at the
corners and mid points of your lot
lines
Adding on to your house: You will
need a Boundary Improvement
Survey with the adjacent houses
located and elevations at the corners
and mid points of your lot lines
IN THE CITY OF DENVER