如果安装过VS2012的话，直接打开一个VS 2012提供的控制台窗口，比如VS2012 x64 Native Tools Command Prompt.
用下面的命令查看程序的头部信息：
gdal_1.8_rtc>dumpbin /HEADERS gdal18.dll
Microsoft (R) COFF/PE Dumper Version 11.00.60610.1
Copyright (C) Microsoft Corporation. All rights reserved.
Dump of file gdal18.dll
PE signature found
File Type: DLL
FILE HEADER VALUES
8664 machine (x64)
6 number of sections
52130233 time date stamp Tue Aug 20 13:44:19 2013
0 file pointer to symbol table
0 number of symbols
F0 size of optional header
2022 characteristics
Executable
Application can handle large (>2GB) addresses
DLL
gdal_1.8_rtc>dumpbin /HEADERS gdal18.dll
Microsoft (R) COFF/PE Dumper Version 11.00.60610.1
Copyright (C) Microsoft Corporation. All rights reserved.
Dump of file gdal18.dll
PE signature found
File Type: DLL
FILE HEADER VALUES
8664 machine (x64)
6 number of sections
52130233 time date stamp Tue Aug 20 13:44:19 2013
0 file pointer to symbol table
0 number of symbols
F0 size of optional header
2022 characteristics
Executable
Application can handle large (>2GB) addresses
DLL
看到x64了么？ 所以这是64位的dll.