You can file a suit for rectification under specific relief act before the civil court for correction in the sale deed. The court shall pass order on same based on the Naksha and all other details.  

You can do the same and rectify the same in presence of Dy registrar.

If seller refuses to execute deed of rectification 

you may file a suit before a court under Section 26 of Specific Relief Act 1963. The law provides for relief to parties in case the real intention of the party is not properly reflected in the documents executed because of a bona fide mistake of fact.

2) . The court can direct the rectification of an instrument, if it is satisfied that the deed does not express the real intention of the parties. This relief is entirely discretionary.

3) There is no specific period of limitation fixed for filing the suit for rectification. Thus the residuary Article- 113 is applicable.you ought to file suit within three years from the date of the sale deed. From the date of the sale deed itself, the time starts to run for filing the suit

1. Rectification deed is the only answer but for this the seller has to be brought on board. 

2. There is nothing such as self declaration. 

First check with the survey record which one is correct. if the earlier sale deed contained the wrong measurement then you need not make any corrections in the present sale deed.

If the mistake is in your sale deed then you will have to make another registered deed called deed of rectification wherein you will have to make declaration of the mistakes done and corrections now made.

Unless both parties present rectification is not possible.   There is an alternate, to file the documents with registrar, registrar will issue notice to both parties, if they fail to appear, registrar may rectify the mistake or may reject it.  you can file appeal against the order of registrar. If appeal is dismissed you need to file suit for declaration and rectification.

issue a public notice inviting objections against rectification of error in sale deed and also call on the sellers to co-operate for registration within the period stated in public notice

public notice is to be given in 2 local newspapers

if no objections are received and seller does not show up then you can proceed for unilateral rectification deed, provided the registration department in your state allows the same 

you just need to annex the certified true copy of the document showing the correct dimensions in your rectification deed and have it registered 

if your buyer is co-operative and does not insist for the rectification then the clarification can be given in the sale deed between you and buyer itself 

Dear Client,

Map is attach to sale deed. In that property description may be right. So actual description of property can ass certain from the map. Otherwise through specific relief act, instrument may be rectified. Court will order the seller to rectify the deed.

If the vendor is not cooperating to execute a registered rectification deed, you may first issue a legal notice to him instructing him to execute a registered rectification deed. If there is no response then you may go ahead with the proposed self declaration and apply for rectification deed, if the sub registrar is not entertaining the same , then you may file a suit seeking specific relief to carry out this rectification and get it rectified through court by registered rectification deed, if the vendor do not turn up even after receiving summons from court.

Dear Sir,

The remedy for your problem is to get issue a legal notice and ask the seller to execute rectification deed. If he did not come forward then you may file suit for declaration and correction of boundaries and it will be decreed on adducing little evidence.