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GPS for Land and Construction Surveying in Kelowna

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Global Positioning Systems (GPS) where originally developed by the US military starting on 1973 with the first satellites being launched in 1978. Originally GPS was limited to military use only but is now accessible to anyone with a GPS receiver. The accuracies that may be obtained from the system depend on the degree of the user’s available access and the complexity of GPS receiver being used.  Using survey grade equipment in a static position with proper technique millimetre level accuracy can be achieved anywhere on or above earth as well as at sea. GPS technology is readily available and used as part of most people’s daily lives. GPS has become a part of daily life to many sectors of business including construction machine control, heavy haul trucking fleet management, cargo ships as well as most new vehicles and smart phones for personal navigation.   Naturally GPS has been well adapted for Land Surveying and Construction Surveying. Land Surveyors GPS instruments and equipment are significantly more accurate than that of a consumer grade handheld unit. GPS equipment is an indispensable tool for any Land Surveyors and Construction Surveying.

How GPS works in a nutshell.

The GPS Navigation System relies on satellites that continually broadcast their location in space and maybe thought of as a control station in space.  GPS receivers use a clock exactly synchronized to the GPS clock system and precisely measure the time delay of a satellite GPS time of transmission to the time the users GPS receiver detects the signal. Time delay multiplied by the mean speed of light along the path of transmission from the satellite to the users GPS receiver will give a range from the satellites known position. The users GPS receiver will have an error or offset so the user is not able to directly measure the range to any satellite, but the ‘Pseudo Range’ which is the actual range with an unknown but instantaneously fixed offset.  Pseudo Range is the clock error times the speed of light. If three ranges are simultaneously observed the users 3-dimensional position can be calculated through triangulation.

There are 4 unknown parameters that need to be solved for a navigation solution. The three coordinates and the receivers clock offset. At least 4 satellites must always be visible with the GPS received wherever the user is on or above the earth.  These satellites must be in good geometric configuration relative to the position of the receiver.  Below is a basic overview of some of the pros and cons of how GPS can be used in Construction and Land Surveying.

GPS offers the following advantages over conventional surveying:

  1. The results from measuring a single line, also referred to as a baseline will yield the distance between the start and end stations as well as well as their component parts such as Northing/Easting and Height or Latitude/Longitude and Height.
  2. No line of sight is required between stations unlike conventional surveying where all stations must have a clear line of sight between a foresight and back sight station. Although a clear sky view is required for the GPS receivers to have a clear path to the satellites.
  3. GPS surveying equipment is extremely weatherproof so observations may occur in any weather, day or night. Even thick fog will not affect GPS measurements.
  4. GPS receivers and current survey data collection software allow for one-person operation. This saves significant time and money.
  5. GPS surveyors do not require a significant amount of technical knowledge for basic operation.
  6. Accurate GPS measurements may take place anywhere on land, sea or air.
  7. Baselines of hundreds of kilometers maybe measured eliminating the need for very extensive geodetic survey networks of conventional survey observations.
  8. Continuous measurement observations may be carried out for real time deformation monitoring on structures such as buildings, dams, bridges, overpasses and landslides.

GPS is not a solution for every survey task and maybe subject to the following difficulties:

  1. A clear sky view is required so that satellites can be observed and tracked.
  2. GPS surveying cannot take place indoors, underwater or underground.
  3. Survey grade receivers are very expensive sometimes as much as 2-3 Total Stations depending on the manufacturer.
  4. The value of GPS heights is not immediately understood and must be understood by the survey technician. The coordinate system of GPS is Earth mass centered, so any position on the earths surface will be relative to some arbitrary defined datum, such as an ellipsoid surface. If the height above the Geoid or Mean Sea Level is required then the separation between then the separation between the chosen ellipsoid and geoid model will have to be calculated. Some data collection and survey software may have a model to help solve this problem.

GPS Systems can broadly be divided into three segments,

  • The Space Segment-The Space Segment consists of satellites om an almost constant orbit at a height of approximately 20,200 kilometres above the earth. This is about three times the radius of the earth and orbit the earth in just under 12 hours. The six orbital planes are equally spaced at 55 degrees to the equator. A satellite may appear for up to 5 hours above the horizon. The GPS constellation is designed so a minimum of 4 satellites are always in view at least 25 degrees above the horizon.  Each satellite has an antenna that transmits the satellites position to the user. Each satellite carries two rubidium and two caesium atomic clocks to ensure precise timing.  GPS receivers broadcast on two L Band carrier frequencies, L1 and L2. The carriers are phase modulated to carry 2 codes known as the P code, Precise code or Precise Positioning Service as well as the C/A or Course/Acquisition code or SPS (Standard Positioning Service). It is relatively simple for the GPS equipment to obtain lock onto the C/A code as it short, simple and repeats 1000 times per second.  The P code is long and complex and this is the key to selective access.  Only users approved by the US Department of Defence can utilize the P code.
  • Control Segment-The control segment is a network of ground stations that continually monitor the velocity and shape of satellites orbit. Monitoring Stations are remote stations each with a very precise GPS receiver, clock, meteorological sensors, data processing and communication. Their function is to is to observe and broadcast satellite navigation messages and satellite clock errors and drifts.
  • User segment-The user segment consists of a GPS receiver with a processor. The processor is basically a microcomputer containing software for processing field data.

A typical GPS equipment setup  for Land Surveying and Construction Surveying typically includes 2-GPS receivers (a base and rover), a tripod to setup the base GPS receiver, a survey range pole to mount the rover GPS receiver and a data collector, similar to a handheld computer with software. This is a standard GPS instrument setup for land surveys in Kelowna.

GPS surveying is a great option for many land surveying tasks in the Kelowna area due to our undulating topography and densely forested areas. For more information on how GPS can be used for Land Surveying in the Kelowna area please consult with a registered British Columbia or Canadian Land Surveyor.

How to choose the best Mapping and Survey Technology for your large-scale mining or mapping project.

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With recent and ever evolving surveying and mapping technology it can be a very daunting task to decide the most appropriate approach to a mapping project. Working with a skilled surveying or mapping firm knowledgeable in the most current technologies is crucial to help the client determine the best approach. If you are looking for a survey company between Vernon and Kelowna some considerations that should be asked by the surveying firm should include:

  • What kind of accuracy is required for the project?
  • Is the data set/deliverable going to be used for conceptual or detailed design work?
  • How dense is the vegetation and tree cover?

The most common solutions for large-scale mapping solutions include:

  • Real Time Kinematic GPS surveys
  • Topographic Surveying
  • Unmanned Aerial Vehicle (UAV) or Unmanned Aerial System (UASs) photogrammetry
  • Unmanned Aerial Vehicle (UAV) or Unmanned Aerial System (UASs) LiDAR
  • Laser Scanning
  • Hydrographic/Bathymetry Surveying

Most large-scale mapping projects include a combination of survey technologies. Below is a brief overview.

Real Time Kinematic (RTK) surveying

RTK surveying is a relative position technique that requires two survey grade GPS receivers. One receiver is static and setup on either a known coordinate or an assumed coordinate that can later be processed to the desired projection and scale. This receiver is known as the Base Station. The second receiver, known as the Rover, is with surveyor and taking the survey measurements. The Rovers position is being calculated Real Time relative to the base position. Multiple rovers can be connected the base station simultaneously collecting data. This is a very accurate mapping technique and provides the a very high confidence level by having ‘boots on the ground’.

GPS Receivers can also be mounted to an ATV or other vehicle and can be set to collect measurements while the vehicle is in motion at defined time or distance intervals. This is a great option for sites that are very accessible.

RTK survey receivers can also be used to complete Bathymetry surveys below water surface. The Rover is linked, usually via. Bluetooth to a survey grade sonar that is constantly measuring the range from the sonar Transducer to the bottom of the water body. Data Collection software is used that collects the depth and the measurement to the GPS antennae. Real time depth measurements are collected for later processing and modeling.

Drone Mapping and Surveying

OSDC offers Drone and Aerial Photomapping services from our Kelowna office. Aerial Mapping Drones allow us to cover vast amounts of area in a very short amount of time with a high level of accuracy. The two main types of Aerial Mapping Services for mining include:

Unmanned Aerial Vehicle (UAV) or Unmanned Aerial System (UASs) photogrammetry mapping

Photogrammetry is the art and science of creating 3D models from photographs.

With recent advancements in the Unmanned Aerial Vehicles (UAVs) or Unmanned Aerial Systems (UASs) it is now possible to very accurately map hundreds of acres of land in a single day.  UAV Mapping is becoming extremely popular for mapping mines, gravel pits, rock quarries and construction sites.  By mounting a camera on an Aerial Vehicle and collecting hundreds of images per acre. The images are stitched together using specialized software to create one large Orthomosaic or Orthophoto by matching and marrying the pixels in each individual image. An Orthophoto is a Geometrically corrected and uniformly scaled image. The main deliverable from this type of mapping include a High Resolution Orthophoto, 3D model and a dense point cloud. This type of mapping can produce a 3D model consisting of hundreds of data points per square meter and is ideally suited to a site that has been stripped of trees and vegetation.

To Orthorectify photogrammetry datasets Ground Control Points (GCPs) are set using either Real Time Kinematic (RTK) or Static GPS observations at aerial markers within the mapping area. These targets are typically large targets with a bullseye that will show up in the Ortho mosaic.

Photogrammetry software takes all the images and matches the pixels in each individual to create an orthoimage or mosaic. The orthoimage is then aligned and scaled to Ground Control Points (GCPs) typically set by Real Time Kinematic (RTK).

We always validate our Photogrammetry projects by taking many RTK GPS measurement at random positions throughout the project. These points are used to provide a high level of confidence in our data sets

Unmanned Aerial Vehicle (UAV) or Unmanned Aerial System (UASs) LiDAR mapping

LiDAR is a remote sensing technique that stands for Light Detection and Ranging. This method uses pulsed laser beams to measure ranges (variable distances) to the earths surface. LiDAR energy can penetrate the forest canopy meaning you are able to take ground measurements in forested areas.  LiDAR technology receives multiple measurement returns meaning models can be created for Tree Canopy Height Models as well as Digital Elevation Model (DEM).

It is very important to do your research prior to hiring a service provider for any surveying or mapping project. Many businesses offer just UAV mapping and sell it as being a one stop solution for all mapping needs. It is important to know the limitations of any technology and even more important to hire a professional, knowledgeable and reputable surveying firm.

OSDC provides Aerial Mapping services throughout Kelowna and all of the Okanagan area including Vernon, Lumby, Peachland, Penticton, Oliver and Osoyoos.

Bathymetric Surveying

Bathymetric surveying techniques allow us to map the underwater surface of a waterbody. Most commonly in mining, bathymetry surveying is used map the floor of tailings ponds. Using bathymetry   surveying techniques, we can produce extremely accurate mapping of the floor to determine important information including sediment buildup and monitoring as well as storage capacity.

The two most common sensors used for bathymetry surveying include:

Single Beam Echosounder

Single Beam Echosounders measure the travel time of a sonar pulse from the unit’s transducer that is set just below the water surface. The unit communicates with a GPS Receiver or a prism communicating with a Robotic Total Station.  The Single Beam Echo Sounder communicates with Data Collection Software which will record Real Time measurements of the bottom surface of a water body.  The system is typically setup on a manned boat or pulled across a river or creek channel using taglines.  The data collection software is set to record either a measurement at either a time or distance interval.

Multi Beam Echosounder

Multi Beam Echosounders emit sound waves in a fan shape. Depths are determined by measuring the time it takes for a sound wave to return to the receiver unit. Multibeam Echosounders are typically used to measure tidal water bodies.

 Topographical Surveying and Mapping

Topographical Surveys are a 2-dimensional plan view representation showing the elevations and surface features of a piece of land.  Due to the inconsistent terrain in Kelowna and the Okanagan valley a detailed topographic survey Is typically the first step in any development project. The main components of a topographical map include:

Contour lines

Contours are a horizontal line connecting points if equal elevation. Using a contour map the steepness of terrain can very easily be interpreted. The closer the lines the steeper the further apart the flatter the land is. Contour intervals are decided upon during the drafting stage depending on the scale of the map and topography.

Surface/Man Made Features

As part of a topographic survey surface features are typically surveyed. These typically include things such as utility boxes, manholes, curbs, light poles, signs, asphalt, services and buildings.

Environmental and Water Features

Creeks, watercourses and vegetated/brushy areas. These areas are typically very sensitive to any type of mining or development work

If you are looking for a topographic survey in Kelowna consider OSDC.

Environmental and Water Features

For modeling purposes it is very critical to pickup surface break lines such as tops and bottoms of banks. These are important features for design proposes as well as creating an accurate contour map.

If you are considering hiring a survey company in Kelowna for a mapping project be certain they are familiar and proficient with the most current surveying technology. Services we offer from our Kelowna office include:

  • Aerial Photomapping Services
  • Aerial Mapping Services
  • Drone Mapping Services
  • Topographic Survey services
  • Bathymetry/Hydrographic surveying services
As Built Surveying

Understanding, Realizing and Dealing with Error

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Opportunity for error exists in everything we do as humans and in every piece of equipment we may use for bc survey. This is especially true in surveying and understating, realizing and dealing with error is an absolute necessity.

An error is a difference between a measured or observed value and the “true” value. Every measurement contains some magnitude of the error. Errors are minimized and kept at an acceptable level by an experienced and skilled survey technician, skillful techniques, and using equipment that is appropriately suited to the task at hand, maintained and accurately calibrated. For the purpose of calculating errors, the “true” value of a dimension is determined statistically after multiple measurements have been taken.

Sources of errors fall into three main categories:

  1. Natural Errors caused by atmospheric conditions such as weather, temperature, the wind, refractions, and unmodelled gravity effects.
  2. Instrument errors caused by imperfections in the constructions and adjustment of the surveying equipment being used.
  3. Human error’s caused by the inability of the survey technician to make exact observations due to limitations of human sight, touch, and hearing.

Classifications of Error:

  1. Mistakes are sometimes called gross errors, but should not be classed at errors at all. They are blunders, often resulting from fatigue or an inexperienced surveyor. Because mistakes are typically large they are usually easy to spot and deal with.
  2. Systematic errors are defined as errors for which the magnitude and algebraic sign can be determined. The fact that these errors can be determined allows for the surveyor to calculate and then apply a correction to the measurement to reduce its effect. It is doubtful, however, whether the entire effect of the systematic error is ever entirely eliminated. Careful calibration of all equipment is an essential part of controlling and eliminating the systematic error. An example of systematic errors is the effect of temperature on a steel tape. If the temperature is warm the tape expands and the length of the tape increases, if the temperature is cold the steel tape shrinks and the length is reduced.
  3. Random errors are associated with the skills and vigilance of the surveyor. Random error is introduced into each measurement mainly because no human can perform perfectly. Random errors should be small and there is no procedure that will compensate for or reduce any one single error. Random errors, possibly due to sloppy work, also tend to cancel out giving the appearance of accurate work despite being highly inaccurate.

For more than 20 years, Okanagan Survey & Design has specialized in providing professional, cost-effective technical solutions for projects. Okanagan Survey & Design provides construction and engineering surveying services only. Contact us with any questions about your project needs.

GPS surveying

GPS Surveying – How it Works

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gps surveying topconGlobal Position Systems (GPS) are an indispensable tool for construction surveyors and land surveyors alike. GPS surveying may best be described as having 3 segments. The space segment, the control segment, and the user segment.

The space segment

The space segment consists of at least 24 satellites at an altitude of approximately 20,000 kilometer from the surface of the earth. The satellites are configured for optimal coverage so at least 4 satellites are visible at one time from any position on earth. The satellites contain extremely precise clocks that allow them to stay synchronized with other satellites and the ground control system. All satellite’s broadcast a unique PRN code (Pseudo Range Noise) that allows the user’s receiver on earth to make time based measurements to a satellite.

The control segment

The control segment consists of monitoring stations continuously tracking GPS at various locations throughout the world, and a master control station in the United States. The control stations transmit and receive data to and from the satellites. The control stations monitor performance, determine their orbits, model the atomic clock behaviour, and inject each satellite with their broadcast data.

The user segment

The user segment includes any equipment equipped with a GPS receiver capable of using GPS signals to determine positioning. In the basic mode the user’s receiver shifts a replica of the PRN code into alignment with the incoming signal from the satellites, and scaling their time shift by the speed of light to determine the distance to each satellite.

You may see GPS systems at work throughout Kelowna doing topographic surveys, construction layout surveys, legal surveying, and land surveying.

For more than 20 years, Okanagan Survey & Design has specialized in providing professional, cost-effective technical solutions for projects. Okanagan Survey & Design provides construction and engineering surveying services only. Contact us with any questions about your project needs.

land surveying companies

Types of Surveyors

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Construction surveying companies and Land Surveying companies alike provide surveying services to the private and public sectors. See below for a brief description of various types of surveyors.  Do your research and decide what type of surveyor is best suited for your project.

British Columbia Land Surveyor (BCLS):

Each province in Canada has a self-governing association representing licensed Land Surveyors. British Columbia Land Surveyors (BCLS) is the designation used by Land Surveyors in BC. Only a commissioned Land Surveyor can determine, locate, define, describe establish or re-establish boundaries. Refer to the British Columbia Land Surveyors Act to determine if you require a British Columbia Land Surveyor.

Canada Lands Surveyor (CLS):

Only a Canada Lands Surveyor is licensed to carry out cadastral surveys on “Canada Lands”. “Canada Lands” include three Canadian territories (Yukon, Northwest Territories, and Nunavut), Federal parks, and Aboriginal reserves, as well as on and under the surface of Canada’s oceans. Refer to the Canada Lands Surveyors Act to determine if you require Canada Lands Surveyor.

Construction Surveying

 

Construction Surveyors:

Construction Surveyors have varied educational backgrounds and experience which may include Land Surveyors specializing in construction surveying, Land Survey technicians, professional engineers, Geomatics technologists, GIS, Bachelor’s degree, or engineering technologists.  Typically a Construction Surveyor has experience working for a Land Surveyor as a technician or a civil engineer as a designer, and has much field experience on construction sites.  Typical services a construction surveyor provides includes construction layout or staking for infrastructure projects, building stakeouts, residential surveys, topography, volumetric surveys, and as built surveys. It is imperative a construction surveyor understands the engineering design elements and constructability as well as understating the survey component.

Engineering Surveyors:

Engineering surveyors provide surveying services to engineers, hydrologists, land owners, and businesses. Services typically include topographic surveys, GIS mapping, Dam surveys, Dam Break Analysis Surveys, Bathymetry, channel surveying, deformation monitoring, test hole pickup, gravel pit volumetric surveys, and site plans for municipal permitting.

For more than 20 years, Okanagan Survey & Design has specialized in providing professional, cost-effective technical solutions for projects. Okanagan Survey & Design provides construction and engineering surveying services only. Contact us with any questions about your project needs.

Topographic Survey

Topographic Survey is Part of Design

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Top 3 Reasons a Topographic Survey is Part of a Sound Design

Today’s building projects come with higher budgets and tighter timelines than ever before. For example, the City of Kelowna has nearly $100 million in active construction projects in development at this time. That doesn’t account for the private projects currently underway. Staying on track and avoiding the domino effect leaves very little room for error when planning a new building project, and mistakes are very expensive!

Avoiding costly errors requires proper advance planning to survey land and a thorough understanding of the landscape of the project. To understand why it’s essential to start every building project with one, let’s examine the top three reasons why a topographic survey is part of a sound design.

Land Can be Like an Iceberg

Existing structures, like utility poles and other buildings for survey land, are easy enough to spot. But that’s only part of the story. It’s what’s going on beneath the surface that can quickly turn a quick building project into a lengthy, expensive one with delays. Taking the time to administer a thorough, professional topographical survey can help project managers avoid the (figurative) landmines that can crop up once construction is underway.

Every Discipline has a Reason for Needing a Topographic Survey

Every project, large or small, involves a multi-disciplinary team of experts. Topographic surveys will be used by engineers, architects, and municipal officials, among other professionals, to ensure that stringent guidelines are met. Starting with a topographic survey can save time and money by providing proof design metrics that are sound from the outset.

Required in Observance of Local Regulations

The Okanagan, and indeed all of BC, is filled with natural beauty that it is our duty to protect. Though a topographic survey may not be explicitly outlined as a legal requirement, one will be required to make sure new projects are in line with provincial rules. For example, the BC Oil & Gas Commission has strict regulations regarding the placement of pipelines in relation to the water supply and other infrastructure. There is no way to comply with these regulations without a detailed, professional topographic survey.

For more than 20 years, Okanagan Survey & Design has specialized in providing professional, cost-effective technical solutions for projects. Contact us with any questions about your project needs.

 

 

construction-surveying

Construction Surveying vs Construction Surveyors

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Construction Surveying is the practice of working hands on with construction crews and guiding them through the construction phase of a project.

Construction Surveying

Contractual documents, consulting engineer, or local bylaw may all have specifications that must be adhered to or the project may be rejected. To meet these requirements of the project various instruments may be employed for Construction Surveying including Total Stations, RTK GPS, Static GPS, Digital levels and terrestrial scanners. Tolerances vary greatly from 2mm on a bridge or building to 30mm on a road subgrade. It is the Construction Surveyors job to asses the task at hand and use the instruments and procedures that will meet the required accuracies with the highest efficiency.

Construction Surveyors

Construction Surveyors analyze, interpret, and implement engineering and architecture drawings into a form that construction crews can use in the field. Construction Surveyors are responsible for the layout of streets, highways, bridges, superstructures, buildings, manholes, pipe mainline, hydrants, catch basins, streetlights, and shallow utilities such as gas and electrical. We have even been hired to layout placement of trees and grapes in orchards and vineyards.

Field layout typically includes leaving a nail or marker at the centre of a feature such as manhole or bridge abutment corner. The stake will also provide a geodetic elevation and a grade to set the feature to the proper elevations. Construction Surveyors also typically offset the construction feature so that construction crews can accurately place the feature once the centre is removed by excavation.

It is also the Construction Surveyors job to protect and if necessary relocate horizontal and vertical control points throughout a construction project. Most projects are designed based on a preliminary topographic survey and the same control must be used referenced throughout the duration of the project.

Once construction is complete an as built survey is typically required and the Engineer will produce “As Constructed Drawings” to verify the project has been built to meet the requirements and specification’s.

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