GetDates <-
function(Lat, Long, Product)
{
if(!any(Product == GetProducts())) stop("Product entered does not match any available products; see ?GetProducts.")
if(!is.numeric(Lat) | !is.numeric(Long)) stop("Lat and Long inputs must be numeric.")
if(length(Lat) != 1 | length(Long) != 1) stop("Incorrect number of Lats and Longs supplied (only 1 coordinate allowed).")
if(abs(Lat) > 90 | abs(Long) > 180) stop("Detected a lat or long beyond the range of valid coordinates.")
getdates.xml <- paste('
<soapenv:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:mod="', daacmodis, '/MODIS_webservice">
<soapenv:Header/>
<soapenv:Body>
<mod:getdates soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<Latitude xsi:type="xsd:float">', Lat, '</Latitude>
<Longitude xsi:type="xsd:float">', Long, '</Longitude>
<Product xsi:type="xsd:string">', Product, '</Product>
</mod:getdates>
</soapenv:Body>
</soapenv:Envelope>',
sep = "")
header.fields <- c(Accept = "text/xml",
Accept = "multipart/*",
'Content-Type' = "text/xml; charset=utf-8",
SOAPAction = "")
reader <- basicTextGatherer()
header <- basicTextGatherer()
curlPerform(url = paste0(daacmodis, "/cgi-bin/MODIS/GLBVIZ_1_Glb_subset/MODIS_webservice.pl"),
httpheader = header.fields,
postfields = getdates.xml,
writefunction = reader$update,
verbose = FALSE)
# Check the server is not down by insepcting the XML response for internal server error message.
if(grepl("Internal Server Error", reader$value())){
stop("Web service failure: the ORNL DAAC server seems to be down, please try again later.
The online subsetting tool (https://daac.ornl.gov/cgi-bin/MODIS/GLBVIZ_1_Glb/modis_subset_order_global_col5.pl)
will indicate when the server is up and running again.")
}
xmlres <- xmlRoot(xmlTreeParse(reader$value()))
datesres <- xmlSApply(xmlres[[1]],
function(x) xmlSApply(x,
function(x) xmlSApply(x,
function(x) xmlSApply(x,xmlValue))))
if(colnames(datesres) == "Fault"){
if(length(datesres['faultstring.text', ][[1]]) == 0){
stop("Downloading from the web service is currently not working. Please try again later.")
}
stop(datesres['faultstring.text', ])
} else{
return(as.vector(datesres))
}
}
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