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Elevation.jl
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Elevation.jl
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## --- ETOPO1 (1 arc minute topography)
"""
```julia
get_etopo([varname])
```
Read ETOPO1 (1 arc minute topography) file from HDF5 storage, downloading
from cloud if necessary.
Available `varname`s (variable names) include:
```
"elevation"
"y_lat_cntr"
"x_lon_cntr"
"cellsize"
"scalefactor"
"reference"
```
Units are meters of elevation and decimal degrees of latitude and longitude.
Reference:
Amante, C. and B.W. Eakins, 2009. ETOPO1 1 Arc-Minute Global Relief Model:
Procedures, Data Sources and Analysis. NOAA Technical Memorandum NESDIS NGDC-24.
National Geophysical Data Center, NOAA. doi:10.7289/V5C8276M.
http://www.ngdc.noaa.gov/mgg/global/global.html
See also: `find_etopoelev`.
## Examples
```julia
julia> get_etopo()
Dict{String, Any} with 6 entries:
"cellsize" => 0.0166667
"scalefactor" => 60
"x_lon_cntr" => [-179.992, -179.975, -179.958, -179.942, -179.925, -1…
"reference" => "Amante, C. and B.W. Eakins, 2009. ETOPO1 1 Arc-Minut…
"y_lat_cntr" => [-89.9917, -89.975, -89.9583, -89.9417, -89.925, -89.…
"elevation" => [-58.0 -58.0 … -58.0 -58.0; -61.0 -61.0 … -61.0 -61.0…
julia> get_etopo("elevation")
10800×21600 Matrix{Float64}:
-58.0 -58.0 -58.0 … -58.0 -58.0 -58.0
-61.0 -61.0 -61.0 -61.0 -61.0 -61.0
-62.0 -63.0 -63.0 -63.0 -63.0 -62.0
-61.0 -62.0 -62.0 -62.0 -62.0 -61.0
⋮ ⋱
-4226.0 -4226.0 -4227.0 -4227.0 -4227.0 -4227.0
-4228.0 -4228.0 -4229.0 -4229.0 -4229.0 -4229.0
-4229.0 -4229.0 -4229.0 -4229.0 -4229.0 -4229.0
```
"""
function get_etopo(varname="")
# Available variable names: "elevation", "y_lat_cntr", "x_lon_cntr",
# "cellsize", "scalefactor", and "reference". Units are meters of
# elevation and decimal degrees of latitude and longitude
# Construct file path
filedir = joinpath(resourcepath,"etopo")
filepath = joinpath(filedir,"etopo1.h5")
# Download HDF5 file from Google Cloud if necessary
if ~isfile(filepath)
@info "Downloading etopo1.h5 from google cloud storage to $filedir"
run(`mkdir -p $filedir`)
Downloads.download("https://storage.googleapis.com/statgeochem/etopo1.references.txt", joinpath(filedir,"etopo1.references.txt"))
Downloads.download("https://storage.googleapis.com/statgeochem/etopo1.h5", filepath)
end
# Read and return the file
return h5read(filepath, "vars/"*varname)
end
export get_etopo
"""
```julia
find_etopoelev([etopo], lat, lon, [T=Float64])
```
Find the elevation of points at position (`lat`, `lon`) on the surface of the
Earth, using the ETOPO1 one-arc-degree elevation model.
Units are meters of elevation and decimal degrees of latitude and longitude.
Reference:
Amante, C. and B.W. Eakins, 2009. ETOPO1 1 Arc-Minute Global Relief Model:
Procedures, Data Sources and Analysis. NOAA Technical Memorandum NESDIS NGDC-24.
National Geophysical Data Center, NOAA. doi:10.7289/V5C8276M.
http://www.ngdc.noaa.gov/mgg/global/global.html
See also: `get_etopo`.
## Examples
```julia
julia> etopo = get_etopo("elevation")
10800×21600 Matrix{Float64}:
-58.0 -58.0 -58.0 … -58.0 -58.0 -58.0
-61.0 -61.0 -61.0 -61.0 -61.0 -61.0
-62.0 -63.0 -63.0 -63.0 -63.0 -62.0
-61.0 -62.0 -62.0 -62.0 -62.0 -61.0
⋮ ⋱
-4226.0 -4226.0 -4227.0 -4227.0 -4227.0 -4227.0
-4228.0 -4228.0 -4229.0 -4229.0 -4229.0 -4229.0
-4229.0 -4229.0 -4229.0 -4229.0 -4229.0 -4229.0
julia> find_etopoelev(etopo, 43.702245, -72.0929)
0-dimensional Array{Float64, 0}:
294.0
```
"""
find_etopoelev(lat,lon) = find_etopoelev(get_etopo(),lat,lon)
find_etopoelev(etopo::Dict, lat, lon) = find_etopoelev(etopo["elevation"], lat, lon)
function find_etopoelev(etopo::AbstractArray, lat, lon, T=Float64)
# Interpret user input
@assert eachindex(lat) == eachindex(lon)
# Scale factor (cells per degree) = 60 = arc minutes in an arc degree
sf = 60
maxrow = 180 * sf
maxcol = 360 * sf
# Create and fill output vector
result = Array{T}(undef,size(lat))
for i ∈ eachindex(lat)
if (-90 <= lat[i] <= 90) && (-180 <= lon[i] <= 180)
# Convert latitude and longitude into indicies of the elevation map array
row = 1 + trunc(Int,(90+lat[i])*sf)
row == (maxrow+1) && (row = maxrow) # Edge case
col = 1 + trunc(Int,(180+lon[i])*sf)
col == (maxcol+1) && (col = maxcol) # Edge case
# Find result by indexing
result[i] = etopo[row,col]
else
# Result is NaN if either input is NaN or out of bounds
result[i] = NaN
end
end
return result
end
export find_etopoelev
## --- SRTM15_PLUS (15 arc second topography)
"""
```julia
get_srtm15plus([varname])
```
Read SRTM15plus file from HDF5 storage (15 arc second topography from the
Shuttle Radar Topography Mission), downloading from cloud if necessary.
Available `varname`s (variable names) include:
```
"elevation"
"y_lat_cntr"
"x_lon_cntr"
"cellsize"
"scalefactor"
"nanval"
"reference"
```
Units are meters of elevation and decimal degrees of latitude and longitude.
Reference: https://doi.org/10.5069/G92R3PT9
See also: `find_srtm15plus`.
## Examples
```julia
julia> get_srtm15plus()
Dict{String, Any} with 7 entries:
"cellsize" => 0.00416667
"scalefactor" => 240
"x_lon_cntr" => [-180.0, -179.996, -179.992, -179.988, -179.983,…
"reference" => "http://topex.ucsd.edu/WWW_html/srtm30_plus.html"
"y_lat_cntr" => [-90.0, -89.9958, -89.9917, -89.9875, -89.9833, …
"nanval" => -32768
"elevation" => Int16[-32768 -32768 … -32768 -32768; 3124 3124 ……
julia> get_srtm15plus("elevation")
43201×86401 Matrix{Int16}:
-32768 -32768 -32768 -32768 … -32768 -32768 -32768
3124 3124 3124 3124 3113 3113 3124
3123 3123 3123 3122 3111 3111 3123
3121 3121 3121 3121 3110 3110 3121
⋮ ⋱ ⋮
-4225 -4224 -4224 -4224 -4224 -4225 -4225
-4223 -4222 -4222 -4223 -4223 -4223 -4223
-4223 -4223 -4223 -4223 -4223 -4223 -4223
-4230 -4230 -4230 -4230 … -4230 -4230 -4230
```
"""
function get_srtm15plus(varname="")
# Available variable names: "elevation", "y_lat_cntr", "x_lon_cntr",
# "nanval", "cellsize", "scalefactor", and "reference". Units are
# meters of elevation and decimal degrees of latitude and longitude
# Construct file path
filedir = joinpath(resourcepath,"srtm15plus")
filepath = joinpath(filedir,"srtm15plus.h5")
# Download HDF5 file from Google Cloud if necessary
if ~isfile(filepath)
@info "Downloading srtm15plus.h5 from google cloud storage to $filedir"
run(`mkdir -p $filedir`)
Downloads.download("https://storage.googleapis.com/statgeochem/srtm15plus.references.txt", joinpath(filedir,"srtm15plus.references.txt"))
Downloads.download("https://storage.googleapis.com/statgeochem/srtm15plus.h5", filepath)
end
# Read and return the file
return h5read(filepath,"vars/"*varname)
end
export get_srtm15plus
"""
```julia
find_srtm15plus([srtm], lat, lon, [T=Float64])
```
Find the elevation of points at position (`lat`, `lon`) on the surface of the
Earth, using the SRTM15plus 15-arc-second elevation model.
Units are meters of elevation and decimal degrees of latitude and longitude.
Reference: https://doi.org/10.5069/G92R3PT9
See also: `get_srtm15plus`.
## Examples
```julia
julia> srtm = get_srtm15plus("elevation")
43201×86401 Matrix{Int16}:
-32768 -32768 -32768 -32768 … -32768 -32768 -32768
3124 3124 3124 3124 3113 3113 3124
3123 3123 3123 3122 3111 3111 3123
3121 3121 3121 3121 3110 3110 3121
⋮ ⋱ ⋮
-4225 -4224 -4224 -4224 -4224 -4225 -4225
-4223 -4222 -4222 -4223 -4223 -4223 -4223
-4223 -4223 -4223 -4223 -4223 -4223 -4223
-4230 -4230 -4230 -4230 … -4230 -4230 -4230
julia> find_srtm15plus(srtm, 43.702245, -72.0929)
0-dimensional Array{Float64, 0}:
252.0
```
"""
find_srtm15plus(lat,lon) = find_srtm15plus(get_srtm15plus(),lat,lon)
find_srtm15plus(srtm::Dict, lat, lon) = find_srtm15plus(srtm["elevation"], lat, lon)
function find_srtm15plus(srtm::AbstractArray, lat, lon, T=Float64)
# Interpret user input
length(lat) != length(lon) && error("lat and lon must be of equal length")
# Scale factor (cells per degree) = 60 * 4 = 240
# (15 arc seconds goes into 1 arc degree 240 times)
sf = 240
# Create and fill output vector
out = Array{T}(undef,size(lat))
for i ∈ eachindex(lat)
if isnan(lat[i]) || isnan(lon[i]) || lat[i]>90 || lat[i]<-90 || lon[i]>180 || lon[i]<-180
# Result is NaN if either input is NaN or out of bounds
out[i] = NaN
else
# Convert latitude and longitude into indicies of the elevation map array
# Note that STRTM15 plus has N+1 columns where N = 360*sf
row = 1 + round(Int,(90+lat[i])*sf)
col = 1 + round(Int,(180+lon[i])*sf)
# Find result by indexing
res = srtm[row,col]
if res == -32768
out[i] = NaN
else
out[i] = res
end
end
end
return out
end
export find_srtm15plus
## --- End of File