Custom Query (125 matches)
Results (43 - 45 of 125)
Ticket | Resolution | Summary | Owner | Reporter | ||||
---|---|---|---|---|---|---|---|---|
#138 | fixed | Clarification of false_easting / false_northing | davidhassell | heiko.klein | ||||
Description |
The explanation of false_easting/northing has left us often puzzled weather false_easting should be added to the existing x-axis values, or subtracted. To clarify this, I suggest the following modification to Table F.1: false_easting
The value applied to all abscissa values in the rectangular coordinates for a map projection. This value frequently is assigned to eliminate negative numbers. Expressed in the unit of the coordinate variable identified by the standard name projection_x_coordinate. The formula to convert from a projection-axis value without false_easting (x0) to a projection-axis value with false_easting is (xf) is: false_northing
The value applied to all ordinate values in the rectangular coordinates for a map projection. This value frequently is assigned to eliminate negative numbers. Expressed in the unit of the coordinate variable identified by the standard name projection_y_coordinate. The formula to convert from a projection-axis value without false_northing (y0) to a projection-axis value with false_northing is (yf) is then: |
|||||||
#139 | fixed | Update to conformance document: standard_names of area_type & region | davidhassell | ros | ||||
Description |
Section 3.3. of the CF convention states: "Some standard names (e.g. region and area_type) are used to indicate quantities which are permitted to take only certain standard values. This is indicated in the definition of the quantity in the standard name table, accompanied by a list or a link to a list of the permitted values." but there is no corresponding statement in the conformance document. I therefore propose to add the following to section 3.3 of the CF Conformance document: "If a variable has a standard_name of region or area_type, it must have value(s) from the permitted list." |
|||||||
#143 | fixed | Supplement the definitions of dimensionless vertical coordinates | davidhassell | jonathan | ||||
Description |
1 TitleSupplement the definitions of dimensionless vertical coordinates 2 ModeratorRich Signell 3 Purposes
4 Status quo and benefitsAt the moment it is difficult for a data user to know exactly what the computed vertical coordinate is. For example, does the ocean sigma coordinate give you a height with respect to a geopotential surface or a reference ellipsoid, and precisely what is that datum e.g. NAVD88? These changes are intended to make it easier. 5 Detailed proposalInsert a new section heading "4.3.3 Parameterized Vertical Coordinate" after the sentence "The units attribute is not required ..." in section 4.3.2. Thus, the remainder of that section, about formula terms etc., will become a new section under the new heading. Amend the existing first paragraph of this new section from the existing text:
to read as follows:
In this section, in the sentence after Example 4.3, change "Appendix D, Dimensionless Vertical Coordinates" to "Appendix D, Parameterized Vertical Coordinates". In section 5.6, replace the existing paragraph
with
In Appendix A, between the entries for compress and Conventions, insert an entry for computed_standard_name, Type S, Use C, Link "Section 4.3.3, Parameterized Vertical Coordinate", Description "Indicates the standard name, from the standard name table, of the parameterized dimensional vertical coordinate values computed according to the formula in the definition." In Appendix A, change the Link for formula_terms to "Section 4.3.3, Parameterized Vertical Coordinate". Rename Appendix D as "Parameterized vertical coordinates". Change the first sentence of Appendix D from "The definitions given here allow an application to compute dimensional coordinate values from the dimensionless ones and associated variables." to "The definitions given here allow an application to compute dimensional coordinate values from the parameterized (usually dimensionless) ones and associated variables." In the first paragraph of Appendix D, change "where term is a keyword" to "where term is a case-insensitive keyword". Append the following as a third paragraph in the preamble of Appendix D:
In the following, it will be noticed that some formula terms do not have defined standard names at the moment. Of course, names could be defined, but it is not essential because their purpose is identifiable from the formula_terms attribute. However, standard_names have been proposed below for constants in the formula which don't depend on level e.g. reference air pressure. Append the following paragraph to the definition of "Atmosphere natural log pressure coordinate":
Append the following paragraph to the definition of "Atmosphere sigma coordinate":
Append the following paragraph to the definition of "Atmosphere hybrid sigma pressure coordinate":
In the definition of "Atmosphere hybrid height coordinate", change "z(n,k,j,i) is the height above the geoid (approximately mean sea level) at gridpoint (k,j,i) and time (n) , orog(n,j,i) is the height of the surface above the geoid" to "z(n,k,j,i) is the height above the datum (e.g. the geoid, which is approximately mean sea level) at gridpoint (k,j,i) and time (n) , orog(n,j,i) is the height of the surface above the datum", and replace the final paragraph "There is no dimensionless ..." with the following.
In the definition of "Atmosphere smooth level vertical (SLEVE) coordinate", change "z(n,k,j,i) is the height above the geoid (approximately mean sea level) at gridpoint (k,j,i) and time (n), ztop is the height of the top of the model" to "z(n,k,j,i) is the height above the datum (e.g. the geoid, which is approximately mean sea level) at gridpoint (k,j,i) and time (n), ztop is the height of the top of the model above the datum", change "the large and small parts of the topography" to "the large-scale and small-scale components of the topography, and a, b1 and b2 are all functions of the dimensionless SLEVE coordinate" (for the sake of clarification), delete the sentence "The hybrid height coordinate for level k is defined as a(k)*ztop" (which appears to be in the wrong section) and append the following paragraph:
In the definition of "Ocean sigma coordinate", replace "z(n,k,j,i) is height, positive upwards, relative to ocean datum (e.g. mean sea level) at gridpoint (n,k,j,i), eta(n,j,i) is the height of the ocean surface, positive upwards, relative to ocean datum at gridpoint (n,j,i)" with "z(n,k,j,i) is height (positive upwards) relative to the datum (e.g. mean sea level) at gridpoint (n,k,j,i), eta(n,j,i) is the height of the sea surface (positive upwards) relative to the datum at gridpoint (n,j,i)", replace "depth(j,i) is the distance from ocean datum to sea floor (positive value) at horizontal gridpoint (j,i)" with "depth(j,i) is the distance (a positive value) from the datum to the sea floor at horizontal gridpoint (j,i)", and append the following paragraph:
In the definition of "Ocean s-coordinate", make the same replacements as for "Ocean sigma coordinate", and append the following paragraph:
In the definition of "Ocean sigma over z coordinate", make the same replacements as for "Ocean sigma coordinate", after "Above depth depth_c there are nsigma layers" insert "and below this depth the levels are surfaces of constant height zlev (positive upwards) relative to the datum" (this definition is omitted in the current text), and append the following paragraph:
In the definition of "Ocean double sigma coordinate", make the same replacements as for "Ocean sigma coordinate" regarding z and depth (there is no eta in this case), and append the following paragraph:
At the end of Appendix D, insert the following table: Table D.1. Consistent sets of values for standard_name and computed_standard_name for the formula terms indicated.
In the conformance document, rename "4.3.2 Dimensionless Vertical Coordinates" to "4.3.3 Parameterized Vertical Coordinate", and append these new requirements:
If this ticket is agreed, the following standard_names will be proposed: air_pressure_at_top_of_atmosphere_model altitude_at_top_of_atmosphere_model reference_air_pressure_for_atmosphere_vertical_coordinate height_above_geopotential_datum_at_top_of_atmosphere_model height_above_geopotential_datum surface_height_above_geopotential_datum sea_surface_height_above_geopotential_datum sea_floor_depth_below_geopotential_datum sea_floor_depth_below_reference_ellipsoid height_above_sea_level Jonathan |