Orthometric heights within the State of California that are based on the North America Vertical Datum of 1988 and conforming to the provisions of this chapter shall be known as “California Orthometric Heights of 1988.” Orthometric heights are commonly referred to as “elevations.”
Chapter 5California Orthometric Heights
Section § 8890
This law states that elevations, technically known as orthometric heights, in California are based on the North America Vertical Datum of 1988. These are officially termed 'California Orthometric Heights of 1988.'
orthometric heights California Orthometric Heights of 1988 North America Vertical Datum of 1988 elevations measurement standard vertical datum geodetic reference height reference system surveying mapping topographic elevations
Section § 8891
This section provides definitions for various terms related to geodetic and spatial reference systems. These include the National Geodetic Survey (NGS), California Spatial Reference Center (CSRC), North American Vertical Datum of 1988 (NAVD88), Global Positioning System (GPS), Federal Geographic Data Committee (FGDC), Federal Geodetic Control Subcommittee (FGCS), California Spatial Reference Network (CSRN), and California Orthometric Heights of 1988 (COH88). Each term is associated with its acronym or description for clarity within this specific legal context.
As used in this chapter:
(a)CA Public Resources Code § 8891(a) “NGS” means National Geodetic Survey or its successor.
(b)CA Public Resources Code § 8891(b) “CSRC” means California Spatial Reference Center or its successor.
(c)CA Public Resources Code § 8891(c) “NAVD88” means North American Vertical Datum of 1988.
(d)CA Public Resources Code § 8891(d) “GPS” means Global Positioning System and includes other, similar space-based systems.
(e)CA Public Resources Code § 8891(e) “FGDC” means the Federal Geographic Data Committee or its successor.
(f)CA Public Resources Code § 8891(f) “FGCS” means the Federal Geodetic Control Subcommittee or its successor.
(g)CA Public Resources Code § 8891(g) “CSRN” means California Spatial Reference Network as defined by Chapter 3 (commencing with Section 8850), “Geodetic Datums and the California Spatial Reference Network.”
(h)CA Public Resources Code § 8891(h) “COH88” means California Orthometric Heights of 1988.
National Geodetic Survey California Spatial Reference Center North American Vertical Datum of 1988 Global Positioning System Federal Geographic Data Committee Federal Geodetic Control Subcommittee California Spatial Reference Network California Orthometric Heights of 1988 geodetic systems spatial reference definitions survey data geographic information systems positioning technology orthometric heights reference datums
Section § 8892
The term “California Orthometric Heights of 1988” or its abbreviations like “COH88” should solely refer to orthometric heights based on NAVD88, following the rules outlined in this chapter.
The phrase “California Orthometric Heights of 1988” or any abbreviation, such as “COH88,” thereof shall be used only in reference to orthometric heights based on NAVD88 and conforming to the provisions of this chapter.
California Orthometric Heights of 1988 COH88 orthometric heights NAVD88 height reference geodetic datum mapping standards elevation measurement surveying terminology chapter provisions conformity requirements height data naming conventions California geodetic standards height system regulations
Section § 8893
This law section states that COH88 values can be shown either in meters or feet. If feet are used, they must be based on the U.S. Survey Foot standard, where one foot equals 1200/3937 meters.
COH88 values shall be expressed in meters and decimals of a meter or in feet and decimals of a foot. When COH88 values are expressed in feet, the “U.S. Survey Foot,” (one foot equals 1200/3937 meters) shall be used as the standard foot.
COH88 values meters decimals of a meter feet decimals of a foot U.S. Survey Foot measurement standard conversion foot to meter standard foot 1200/3937 meters
Section § 8894
This law section explains that COH88 values can be measured in two different ways. If these values are determined through differential leveling surveys, they are called "leveled COH88" values. If they are determined by using GPS surveys along with a geoid model, they are referred to as "derived COH88" values.
COH88 values that are determined from differential leveling surveys shall be known as “leveled COH88” values. COH88 values that are determined from GPS surveys and the appropriate application of a geoid model shall be known as “derived COH88” values.
COH88 values differential leveling surveys leveled COH88 GPS surveys geoid model derived COH88 surveying methods altitude measurement geospatial data topographical surveys geoid elevation data land surveying geodetic science mapping technology
Section § 8895
The law states that when calculating COH88 values using a geoid model, you must use the most recent version released by the National Geodetic Survey (NGS).
When a geoid model is used to determine derived COH88 values, it shall be the latest geoid model published by NGS.
geoid model COH88 values latest geoid National Geodetic Survey NGS geodetic model version determine values survey technology geodesy coordinate systems mapping standards NGS publications geospatial data geodetic calculations
Section § 8896
This law suggests improving the accuracy of COH88 value calculations by making a local adjustment to the geoid height, based on the most current geoid model provided by the National Geodetic Survey (NGS).
The accuracy of derived COH88 values may be improved by applying a “local orthometric height correction” to the geoid height determined from the latest, applicable geoid model published by NGS.
COH88 values local orthometric height correction geoid height geoid model National Geodetic Survey NGS model accuracy improvement derived values height adjustment geodetic data calculation accuracy orthometric correction geoid model application latest geoid model NGS publications
Section § 8897
This section outlines the requirements for surveys that establish COH88 (California Orthometric Height 88) values, which relate to the precise measurement of land elevations. The survey must connect to a recognized height reference station, which can be a CSRN station, a qualified geodetic control station outside California, or an existing COH88 station shown on specific maps or public documents that meet particular criteria. Importantly, if survey accuracy is claimed, it must adhere to certain accuracy standards set by federal guidelines.
The survey that establishes a COH88 value or values shall meet all of the following requirements:
(a)CA Public Resources Code § 8897(a) The survey shall be referenced to and shall have field-observed statistically independent connections to one or more orthometric height reference stations that is or are one of the following:
(1)CA Public Resources Code § 8897(a)(1) CSRN station.
(2)CA Public Resources Code § 8897(a)(2) Geodetic control station located outside of the State of California that meets all the requirements for inclusion in the CSRN except that the station is outside California.
(3)CA Public Resources Code § 8897(a)(3) Existing COH88 station that (A) is shown on a map filed with the applicable county surveyor by a public officer, subdivision map, corner record, or record of survey, (B) meets all the requirements for inclusion in the CSRN, except that the station and its data are not published by NGS or CSRC, and (C) has an accuracy, conforming to the applicable CSRN requirements, stated for the station’s value.
(4)CA Public Resources Code § 8897(a)(4) Existing COH88 station that is shown on a public map or document that (A) is compiled and maintained by the applicable county surveyor, (B) meets all the requirements for inclusion in the CSRN except that the station and its data are not published by NGS or CSRC, and (C) has an accuracy, conforming to the applicable CSRN requirements, stated for the station’s value.
(b)CA Public Resources Code § 8897(b) If an accuracy is to be claimed for the COH88 value or values established, the claimed accuracy shall be an accuracy standard published by FGDC or FGCS.
COH88 survey orthometric height height reference stations CSRN station geodetic control station California Orthometric Height FGDC standards FGCS standards elevation measurement land surveys survey accuracy public maps county surveyor statistically independent connections orthometric height reference
Section § 8898
This law outlines the documentation requirements for claiming the accuracy of COH88 values, which are specific survey results. When claiming accuracy, the survey must be recorded in a map or document that includes several key details. It must show the COH88 value for each station, whether each value is leveled or derived, and the dates or model used for calculations. If a local correction model is used, data supporting its validity must be included. The documentation must also state the accuracy standard and provide detailed information justifying the standard, including the equipment, methodologies, and data used in the survey.
If an accuracy is claimed for a COH88 value or values, the survey that established the value or values shall be documented on a map, record of survey, corner record, or other document that includes, at a minimum, the following:
(a)CA Public Resources Code § 8898(a) For each COH88 station, the resultant COH88 value.
(b)CA Public Resources Code § 8898(b) For each individual COH88 value, whether it is a leveled COH88 or a derived COH88 value.
(c)CA Public Resources Code § 8898(c) For leveled COH88 values, the beginning and ending dates of the observations used to determine the values.
(d)CA Public Resources Code § 8898(d) For derived COH88 values, the date of the NGS geoid model used to determine the values.
(e)CA Public Resources Code § 8898(e) When derived COH88 values are shown and reflect the application of a “local orthometric height correction model,” written data that justifies the model’s validity. Such written data shall include a summary of the procedures, computations, analysis, and validation process used to develop the model.
(f)CA Public Resources Code § 8898(f) For derived COH88 values, the epoch (date), in a decimal year format to two decimal places, that is the basis of the COH88 values shown. Said epoch shall be the published NGS or CSRC epoch of a controlling station for the survey.
(g)CA Public Resources Code § 8898(g) The FGDC or FGCS accuracy standard of the COH88 value or values established. FGDC accuracies shall be identified as either a local or network accuracy.
(h)CA Public Resources Code § 8898(h) Additional written data that justifies the FGDC or FGCS accuracy standard shown. Such additional written data shall include observation equipment, control diagram including required field-observed statistically independent connection or connections, adjustment methodology and software used, a summary of the procedures used or a reference to a published commonly accepted procedural specifications, final residuals or closures, and other data essential for others to evaluate the survey.
COH88 value documentation accuracy claims leveled COH88 derived COH88 NGS geoid model local orthometric height correction model FGDC accuracy standard survey documentation epoch date accuracy justification observation equipment control diagram survey adjustment methodology accuracy validation survey procedures
Section § 8899
If any document displays COH88 orthometric height values, it must clearly state that the heights are COH88 values and mention any exceptions. Additionally, the document should specify the reference stations that the COH88 values connect to, including their height values and the stated accuracy levels of those stations.
When a COH88 value or values are shown on any document, the document shall include the following:
(a)CA Public Resources Code § 8899(a) A statement that the orthometric height or heights shown are a COH88 value or values; exceptions shall be noted.
(b)CA Public Resources Code § 8899(b) The station or stations to which the COH88 value or values are referenced and connected and the orthometric height value or values and the published or stated accuracy or accuracies of said referenced station or stations.
COH88 value orthometric height reference stations document requirements height accuracy height data exception published accuracy stated accuracy height connection geodetic data surveying height height reference mapping standards topographic data data documentation
Section § 8900
You don't have to use COH88—it’s your choice whether you want to use it or not. This applies to individuals, businesses, and even government agencies.
The use of COH88 by any person, firm, or governmental agency is optional.
COH88 optional use individuals businesses government agencies personal choice flexibility voluntary not mandatory discretionary use compliance option freedom to choose
Section § 8901
This law section ensures that the rules within this chapter do not change or invalidate existing land titles, legal descriptions, or boundaries, nor do they affect how datums or elevations are referenced or used, unless specified otherwise in another section (Section 8892).
This chapter does not impair or invalidate land titles, legal descriptions, or jurisdictional or land boundaries and, further, this chapter does not impair or invalidate references to, or the use of, datums, elevations, orthometric heights, or other height values that do not conform to this chapter except as specified in Section 8892 in this chapter.
land titles legal descriptions jurisdictional boundaries land boundaries datums elevations orthometric heights height values Section 8892 boundary law land survey reference standards property law topographic data
Section § 8902
This law allows the use of new and innovative surveying technologies or methods even if there are no official specifications or guidelines available for them yet.
This chapter does not prohibit the use of new surveying technologies or techniques for which FGCS specifications or other accepted specifications have not yet been published.
new surveying technologies innovative surveying methods FGCS specifications acceptance of new technology surveying guidelines technological advancement in surveying lack of published specifications innovation in surveying future surveying techniques surveying tools unpublished standards surveying industry updates technology in land surveying advancements in measurement techniques
