Keith Vetter 2005-06-15 :
Can you find your house?
As part of Google Maps, Google recently acquired Keyhole and all its satellite images. This applet lets you view individual images at various locations and zoom levels.
The url to a given images is a quad-tree descent path. Put in English, it's like this:
My house has the quad path tqstqqrtstrqrqq.
====
#!/bin/sh
# Restart with tcl: -*- mode: tcl; tab-width: 8; -*- \
exec tclsh $0 ${1+"$@"}
##+##########################################################################
#
# MyHouse.tcl - gets satellite images from Google at deeper resolution
# by Keith Vetter, June 15, 2005
#
# See About for an explanation. NB. the second stage map is weird
#
package require Tk
package require http
package require Img
array set S {title "My House" quad "t" west -180 east 180 north 90 south -90}
set S(url) "http://kh.google.com/kh?v=1&t="
array set D {0 {south east q} 1 {south west r} 2 {north east t} 3 {north west s}}
proc DoDisplay {} {
wm title . $::S(title)
pack [frame .ctrl -relief ridge -bd 2 -padx 5 -pady 5] \
-side right -fill both -ipady 5
pack [frame .top -relief raised -bd 2] -side top -fill x
pack [frame .screen -bd 2 -relief raised] -side top -fill both -expand 1
canvas .c -height 256 -width 256 -bd 0 -highlightthickness 0
label .msg -textvariable ::S(quad) -bd 2 -bg white -relief ridge
pack .msg -in .screen -side bottom -fill both
pack .c -in .screen -side top -fill both -expand 1
catch {image delete ::img::map}
image create photo ::img::map ;#-width 256 -height 256
.c create image 0 0 -anchor nw -image ::img::map
.c create line 0 128 256 128 -fill white -dash 1
.c create line 128 0 128 256 -fill white -dash 1
bind .c <Button-1> [list Click %x %y]
bind all <Key-F2> {console show}
DoCtrlFrame
.msg config -font [.reset cget -font]
}
proc DoCtrlFrame {} {
set row -1
foreach v {north south east west equator meridian} {
if {[incr row] == 4} {incr row}
label .$v -text "[string totitle $v]:" -anchor e
label .v$v -textvariable S(p,$v) -bd 2 -relief sunken
grid .$v .v$v -in .ctrl -row $row -sticky ew
}
button .reset -text Reset -command Reset -bd 4
.reset configure -font "[font actual [.reset cget -font]] -weight bold"
option add *Button.font [.reset cget -font]
button .undo -text Undo -command Undo -bd 4
button .about -text About -command About
grid rowconfigure .ctrl 4 -minsize 20
grid rowconfigure .ctrl 50 -weight 1
grid .undo - -in .ctrl -row 100 -sticky ew
grid .reset - -in .ctrl -row 101 -sticky ew
grid rowconfigure .ctrl 102 -minsize 10
grid .about - -in .ctrl -row 103 -sticky ew
PrettyLats
}
proc Click {x y {noGUI 0}} {
foreach {lat lon quad} $::D([expr {($x > 128) + 2*($y > 128)}]) break
set ::S($lon) [expr {($::S(east) + $::S(west))/2.0}]
if {[string length $::S(quad)] == 2} {
set quad [string map {q t t q r s s r} $quad]
}
if {[string length $::S(quad)] != 1} {
set ::S($lat) [expr {($::S(north) + $::S(south))/2.0}]
}
append ::S(quad) $quad
if {! $noGUI} GetImage
}
proc GetImage {} {
. config -cursor watch
set url "$::S(url)$::S(quad)"
set token [::http::geturl $url]
::http::wait $token
set data [::http::data $token]; list
::http::cleanup $token
::img::map config -data $data
if {[string length $::S(quad)] == 2} SwapHalves
PrettyLats
. config -cursor {}
.undo config -state [expr {$::S(quad) eq "t" ? "disabled" : "normal"}]
}
proc PrettyLats {} {
set ::S(meridian) [expr {($::S(east) + $::S(west))/2.0}]
set ::S(equator) [expr {($::S(north) + $::S(south))/2.0}]
foreach v {north south east west meridian equator} {
set ::S(p,$v) [PrettyLat $::S($v)]
}
}
proc PrettyLat {lat} {
set deg [expr {int($lat)}]
set frac [expr {($lat - $deg)*60}]
set min [expr {int($frac)}]
set sec [expr {($frac - $min)*60}]
return [format "% 3d\xB0 %02d' %.2g\x22" $deg $min $sec]
}
proc Reset {} {
array set ::S {quad "t" west -180 east 180 north 90 south -90}
GetImage
}
proc SwapHalves {} {
image create photo ::img::tmp -width 256 -height 256
::img::tmp copy ::img::map -from 0 0 256 128 -to 0 128
::img::tmp copy ::img::map -from 0 128 256 256 -to 0 0
::img::map copy ::img::tmp
image delete ::img::tmp
}
proc Undo {} {
array set Q {q {0 0} r {200 0} s {200 200} t {0 200}}
set quads [split [string range $::S(quad) 1 end-1] ""]
array set ::S {quad "t" west -180 east 180 north 90 south -90}
set cnt -1
foreach quad $quads {
incr cnt
set q $quad
if {$cnt == 1} {
set quad [string map {q t t q r s s r} $quad]
}
foreach {x y} $Q($quad) break
Click $x $y 1
}
GetImage
}
proc where {wlat wlon} {
global S
set top "top"
if {$wlat < $S(equator)} { set top "bottom"}
set left "right"
if {$wlon < $S(meridian)} {set left "left"}
set where "$top $left"
puts $where
return $where
}
proc About {} {
set msg "$::S(title)\nby Keith Vetter, June 15, 2005\n\n"
append msg "Can you find your house?\n\n"
append msg "This applet lets you view satellite images from\n"
append msg "Google's recently Keyhole imagery data set.\n\n"
append msg "The url for an actual image represents a quad-tree\n"
append msg "descent path. Put in English, it's like this:\n"
append msg " o start with the whole world:\n"
append msg " http://kh.google.com/kh?v=1&t=t\n"
append msg " o select a quadrant, adding q, r, s or t to the URL\n"
append msg " for top left, top right, bottom right, bottom left\n"
append msg " o repeat\n\n"
append msg "My house is at:\n"
append msg " http://kh.google.com/kh?v=1&t=tqstqqrtstrqrqq"
tk_messageBox -title "About $::S(title)" -message $msg
}
DoDisplay
Reset
update
wm geom . [wm geom .]
return====